Editor's Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to authors, or important in this field. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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Article
Biological Ice Nucleators in Snow Samples from Greece
Atmosphere 2021, 12(11), 1461; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12111461 - 05 Nov 2021
Abstract
The formation of precipitation in clouds is initiated by inorganic and organic/biological ice nuclei. Certain species of bacteria and fungi are known to act as efficient biological ice nuclei at temperatures between −10 and 0 °C. Biological ice nuclei have been found and [...] Read more.
The formation of precipitation in clouds is initiated by inorganic and organic/biological ice nuclei. Certain species of bacteria and fungi are known to act as efficient biological ice nuclei at temperatures between −10 and 0 °C. Biological ice nuclei have been found and characterized in precipitation samples (snow, rain, and hail). We investigated the presence of warm temperature biological ice nuclei in 17 fresh snow samples from Greece and isolated and partially characterized ice nucleation active bacteria from these. All snow samples contained particles or other material active as ice nuclei at −9 °C in concentrations ranging from 3 to 943 nuclei/L. The numbers of this class of ice nuclei were reduced or eliminated after incubating snowmelt concentrates at 100 °C for 15 min and by treatment with lysozyme, a bacterial cell wall-degrading enzyme. These findings indicate the presence of microbial ice nuclei in snow samples from Greece. We also isolated ice nucleation active bacteria from some of the samples. These bacteria belong to genus Pseudomonas and are common on plants and soil. This is the first report on biological ice nuclei in precipitation samples from Greece. Full article
(This article belongs to the Special Issue Bioaerosols: Composition, Meteorological Impact, and Transport)
Article
Bacterial Characteristics of Dust Particle Saltation in Gobi Dust Sites, Mongolia
Atmosphere 2021, 12(11), 1456; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12111456 - 03 Nov 2021
Abstract
The Gobi Desert is a major source of Asian dust events, and the resulting health hazards have increased significantly in recent years. We reported that a variety of live bacteria were distributed in the Gobi Desert in relation to land use. Bacterial distribution [...] Read more.
The Gobi Desert is a major source of Asian dust events, and the resulting health hazards have increased significantly in recent years. We reported that a variety of live bacteria were distributed in the Gobi Desert in relation to land use. Bacterial distribution was confirmed in the environment and on the land used by animals; however, bacterial saltation due to dust events has not been investigated in detail. In this study, to understand the distribution of surface bacteria in the atmosphere by dust saltation, live bacteria in four dust-generating areas in the Gobi area were monitored using an artificial dust generating device. The live bacteria were detected by experimental saltation at a wind speed of 6.5–8 m/s in all areas. A certain number of live bacteria are constantly saltated by dust events, and these bacteria depend on land use. Moreover, the bacterial saltation strain depended on land use and diversity, indicating that live bacteria are lifted into the environment by dust events. These findings indicate that dust events saltate environmental bacteria on the ground, suggest the risk of animal-derived bacterial saltation affected by land use, and present cross-border public health challenges to be considered in the future. Full article
(This article belongs to the Section Air Quality)
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Article
Optimization of HPC Use for 3D High Resolution Urban Air Quality Assessment and Downstream Services
Atmosphere 2021, 12(11), 1410; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12111410 - 26 Oct 2021
Abstract
The number of cities, or parts of cities, where air quality has been computed using the PMSS 3D model now appears to be sufficient to allow assessment and understanding of performance. Two fields of application explain the growing number of sites: the first [...] Read more.
The number of cities, or parts of cities, where air quality has been computed using the PMSS 3D model now appears to be sufficient to allow assessment and understanding of performance. Two fields of application explain the growing number of sites: the first is the long-term air quality assessment required in urban areas for any building or road project. The geometric complexity found in such areas can justify the use of a 3D approach, as opposed to Gaussian ones. However, these studies have constraining rules that can make the modelling challenging: several scenarios are needed (current, future with project, future without project), the long-term impact implies a long physical time period to be computed, and the spatial extension of the domain can be large in order to cover the traffic impact zone of the project. The second type of application is dedicated to services and, essentially, to forecasting. As for impact assessments, the modelling can be challenging here because of the extension of the domain if the target area is a whole city. Forecast also adds the constraint of time, as results are requested early, and the constraint of robustness. The CPU amount needed to meet all these requirements is important. It is therefore crucial to optimize all possible parts of the modelling chain in order to limit cost and delay. The sites presented in the article have been modelled with PMSS for long periods. This allows feedback to be provided on different topics: (a) daily forecasts offer an opportunity to increase the robustness of the modelling chain; (b) quantitative validation at air quality measurement stations; (c) comparison of annual impact based on a whole year, and based on a sampling list of dates selected thanks to a classification process; (d) large calculation domains with widespread pollutant emissions offer a great opportunity to qualitatively check and improve model results on numerous geometrical configurations; (e) CPU time variations between different sites provide valuable information to select the best parametrizations, to predict the cost of the services, and to design the needed hardware for a new site. Full article
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Article
Sulfur and Nitrogen Oxides in the Atmosphere of Lake Baikal: Sources, Automatic Monitoring, and Environmental Risks
Atmosphere 2021, 12(10), 1348; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101348 - 15 Oct 2021
Abstract
This paper analyzes the results of the automatic (in situ) recording of the regional transport of pollutants from the large regional coal-fired thermal power plants in the atmospheric boundary layer above the southern basin of Lake Baikal. Due to high stacks (about 200 [...] Read more.
This paper analyzes the results of the automatic (in situ) recording of the regional transport of pollutants from the large regional coal-fired thermal power plants in the atmospheric boundary layer above the southern basin of Lake Baikal. Due to high stacks (about 200 m), emissions from large thermal power plants rise to the altitudes of several hundreds of meters and spread over long distances from their source by tens and hundreds of kilometers. The continuous automatic monitoring of the atmosphere in the southern basin of Lake Baikal on top of the coastal hill (200 m above the lake) revealed the transport of a large number of sulfur oxides and nitrogen oxides in the form of high-altitude plumes from thermal power plants of the large cities located 70 to 100 km to the northwest of the lake (Irkutsk and Angarsk). The consequence of such transport is the increased acidity of precipitation in the southern basin of Lake Baikal and the additional influx of biogenic nitrogen compounds to the lake ecosystem. The spatial scale and possible risks of such regional transport of air pollution for the lake ecosystem require further closer study. Full article
(This article belongs to the Special Issue Air Quality Management)
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Article
Comparing Four Types Methods for Karst NDVI Prediction Based on Machine Learning
Atmosphere 2021, 12(10), 1341; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101341 - 13 Oct 2021
Abstract
As a link for energy transfer between the land and atmosphere in the terrestrial ecosystem, karst vegetation plays an important role. Karst vegetation is not only affected by environmental factors but also by intense human activities. The nonlinear characteristics of vegetation growth are [...] Read more.
As a link for energy transfer between the land and atmosphere in the terrestrial ecosystem, karst vegetation plays an important role. Karst vegetation is not only affected by environmental factors but also by intense human activities. The nonlinear characteristics of vegetation growth are induced by the interaction mechanism of these factors. Previous studies of this relationship were not comprehensive, and it is necessary to further explore it using a suitable method. In this study, we selected climate, human activities, topography, and soil texture as the response factors; a nonlinear relationship model between the karst normalized difference vegetation index (NDVI) and these factors was established by applying a back propagation neural network (BPNN), a radial basis function neural network (RBFNN), the random forest (RF) algorithm, and support vector regression (SVR); and then, the karst NDVI was predicted. The coefficient of determination (R2), mean square error (MSE), root mean square error (RMSE), and mean absolute percentage error (MAPE) of the obtained results were calculated, and the mean R2 values of the BPNN, RBFNN, RF, and SVR models were determined to be 0.77, 0.86, 0.89, and 0.91, respectively. Compared with the BPNN, RBFNN, and RF models, the SVR model had the lowest errors, with mean MSE, RMSE, and MAPE values of 0.001, 0.02, and 2.77, respectively. The results show that the BPNN, RBFNN, RF, and SVR models are within acceptable ranges for karst NDVI prediction, but the overall performance of the SVR model is the best, and it is more suitable for karst vegetation prediction. Full article
(This article belongs to the Special Issue Application of Remote Sensing Cloud Computing in Land Surface Change)
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Article
Indoor Air Quality in Healthcare and Care Facilities: Chemical Pollutants and Microbiological Contaminants
Atmosphere 2021, 12(10), 1337; https://doi.org/10.3390/atmos12101337 - 13 Oct 2021
Cited by 1
Abstract
The indoor air quality of healthcare and care facilities is poorly studied. The aim of this study was to qualitatively and quantitatively describe the chemical pollution and the microbiological contaminations of the indoor environment of these facilities. Methods: A wide range of chemical [...] Read more.
The indoor air quality of healthcare and care facilities is poorly studied. The aim of this study was to qualitatively and quantitatively describe the chemical pollution and the microbiological contaminations of the indoor environment of these facilities. Methods: A wide range of chemical compounds (39 volatile and 13 semi-volatile organic compounds, carbon dioxide, fine particulate matter) and microorganisms (fungi and bacteria) were studied. Sampling campaigns were conducted in two French cities in summer 2018 and winter 2019 in six private healthcare facilities (general practitioner’s offices, dental offices, pharmacies) and four care facilities (nursing homes). Results: The highest median concentrations of chemical compounds (μg/m3) were measured for alcohols (ethanol: 378.9 and isopropanol: 23.6), ketones (acetone: 18.8), aldehydes (formaldehyde: 11.4 and acetaldehyde: 6.5) and terpenes (limonene: 4.3). The median concentration of PM2.5 was 9.0 µg/m3. The main bacteria of these indoor environments were Staphylococcus, Micrococcus and Bacillus genera, with median bacterial concentrations in the indoor air of 14 cfu/m3. The two major fungal genera were Cladosporium and Penicillium, with median fungal concentrations of 7 cfu/m3. Conclusions: Indoor air in healthcare and care facilities contains a complex mixture of many pollutants found in higher concentrations compared to the indoor air in French hospitals in a previous study. Full article
(This article belongs to the Special Issue Chemical Speciation Monitoring and Measurement)
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Article
Generating Flood Hazard Maps Based on an Innovative Spatial Interpolation Methodology for Precipitation
Atmosphere 2021, 12(10), 1336; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101336 - 13 Oct 2021
Abstract
In this study, a new approach for rainfall spatial interpolation in the Luxembourgian case study is introduced. The method used here is based on a Fuzzy C-Means (FCM) clustering method. In a typical FCM procedure, there are a lot of available data and [...] Read more.
In this study, a new approach for rainfall spatial interpolation in the Luxembourgian case study is introduced. The method used here is based on a Fuzzy C-Means (FCM) clustering method. In a typical FCM procedure, there are a lot of available data and each data point belongs to a cluster, with a membership degree [0 1]. On the other hand, in our methodology, the center of clusters is determined first and then random data are generated around cluster centers. Therefore, this approach is called inverse FCM (i-FCM). In order to calibrate and validate the new spatial interpolation method, seven rain gauges in Luxembourg, Germany and France (three for calibration and four for validation) with more than 10 years of measured data were used and consequently, the rainfall for ungauged locations was estimated. The results show that the i-FCM method can be applied with acceptable accuracy in validation rain gauges with values for R2 and RMSE of (0.94–0.98) and (9–14 mm), respectively, on a monthly time scale and (0.86–0.89) and (1.67–2 mm) on a daily time scale. In the following, the maximum daily rainfall return periods (10, 25, 50 and 100 years) were calculated using a two-parameter Weibull distribution. Finally, the LISFLOOD FP flood model was used to generate flood hazard maps in Dudelange, Luxembourg with the aim to demonstrate a practical application of the estimated local rainfall return periods in an urban area. Full article
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Article
Spectral Recalibration of NOAA HIRS Longwave CO2 Channels toward a 40+ Year Time Series for Climate Studies
Atmosphere 2021, 12(10), 1317; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101317 - 09 Oct 2021
Abstract
The High-Resolution Infrared Radiation Sounder (HIRS) on NOAA and MetOp A/B satellites has been observing the Earth continuously for over four decades, providing essential data for operational numerical weather prediction, retrieval of atmospheric vertical profile, and total column information on atmospheric temperature, moisture, [...] Read more.
The High-Resolution Infrared Radiation Sounder (HIRS) on NOAA and MetOp A/B satellites has been observing the Earth continuously for over four decades, providing essential data for operational numerical weather prediction, retrieval of atmospheric vertical profile, and total column information on atmospheric temperature, moisture, water vapor, ozone, cloud climatology, and other geophysical parameters globally. Although the HIRS data meets the needs of the short-term weather forecast, there are inconsistencies when the long-term decadal time series is used for time series analysis. The discrepancies are caused by several factors, including spectral response differences between the HIRS models on the satellites and spectral response uncertainties and other calibration issues. Previous studies have demonstrated that significant improvements can be achieved by recalibrating some of the HIRS longwave CO2 channels (Channels 4, 5, 6, and 7), which has helped make the time series more consistent. The current study aims to extend the previous study to the remaining longwave infrared sounding channels, including Channels 1, 2, 3, and 8, using a similar approach. Similar to previous findings, the spectral shift of the HIRS bands has helped improve the consistency in the time series from NOAA-06 to MetOp-A and B for these channels. We also found that HIRS channels on MetOp-B also have bias relative to Infrared Atmospheric Sounding Interferometer (IASI) on the same satellite, especially Channel 4, and a spectral shift significantly reduced the bias. To bridge the observation gap in time series in the mid-1980s between NOAA-07 and NOAA-09, the global mean method has been used since no transfer radiometers between them was available for this period, and the spectral response function corrections, therefore, can be applied to the earliest satellites (NOAA-06) for these channels. The recalibration parameters have been provided to other scientists at the University of Wisconsin for improving the time series in their long-term studies using historical HIRS data and are now made available to the science community. Full article
(This article belongs to the Special Issue Advanced Technologies in Satellite Observations)
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Article
A GPU-Accelerated Radiation Transfer Model Using the Lattice Boltzmann Method
Atmosphere 2021, 12(10), 1316; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101316 - 09 Oct 2021
Abstract
A prototype of a three-dimensional (3-D) radiation model is developed using the lattice Boltzmann method (LBM) and implemented on a graphical processing unit (GPU) to accelerate the model’s computational speed. This radiative transfer-lattice Boltzmann model (RT-LBM) results from a discretization of the radiative [...] Read more.
A prototype of a three-dimensional (3-D) radiation model is developed using the lattice Boltzmann method (LBM) and implemented on a graphical processing unit (GPU) to accelerate the model’s computational speed. This radiative transfer-lattice Boltzmann model (RT-LBM) results from a discretization of the radiative transfer equation in time, space, and solid angle. The collision and streaming computation algorithm, widely used in LBM for fluid flow modeling, is applied to speed up the RT-LBM computation on the GPU platform. The isotropic scattering is assumed in this study. The accuracy is evaluated using Monte Carlo method (MCM) simulations, showing RT-LBM is quite accurate when typical atmospheric coefficients of scattering and absorption are used. RT-LBM runs about 10 times faster than the MCM in a same CPU. When implemented on a NVidia Tesla V100 GPU in simulation with a large number of computation grid points, for example, RT-LBM runs ~120 times faster than running on a single CPU. The test results indicate RT-LBM is an accurate and fast model and is viable for simulating radiative transfer in the atmosphere with ranges for the isotropic atmosphere radiative parameters of albedo scattering (0.1~0.9) and optical depth (0.1~12). Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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Article
Exposure to Particles and Gases in a Shopping Mall: Spatial Heterogeneity and Outdoor Infiltration
Atmosphere 2021, 12(10), 1313; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101313 - 08 Oct 2021
Abstract
Shopping malls in Hong Kong are usually located near major roads. Indoor air quality (IAQ) in these buildings is subject to infiltration of outdoor traffic-related pollutants, such as PM10, PM2.5, CO, and NO2. Furthermore, the existence of indoor sources and building [...] Read more.
Shopping malls in Hong Kong are usually located near major roads. Indoor air quality (IAQ) in these buildings is subject to infiltration of outdoor traffic-related pollutants, such as PM10, PM2.5, CO, and NO2. Furthermore, the existence of indoor sources and building geometry added to the complexity of variations in IAQ. To understand outdoor infiltration and spatial heterogeneity of these pollutants, we conducted fixed and cruise indoor sampling, together with simultaneous outdoor measurements, in a typical mall in Hong Kong. The cruise sampling was conducted indoors on a predesigned route and repeated 15 times. Outdoor infiltration was quantified based on regression analysis between indoor and outdoor sampling. Results showed that 75% of PM2.5, 53% of PM10, and 59% of NO2 were infiltrated into the mall during opening hours. Elevated PM2.5 and CO were observed during the dinner period, suggesting an impact from cooking. Substantial spatial variations were observed for PM10, PM2.5, and NO2, particularly at locations near entrances and restaurants. Measures are needed to reduce pollution intrusion from building openings and cooking-related sources to improve air quality in the selected mall. Fixed and cruise sampling methods used in this study provide insights on sensor deployment for future air quality monitoring in buildings. Full article
(This article belongs to the Special Issue Field Measurement for Thermal Comfort and Indoor Air Quality)
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Article
Equivalent Black Carbon Aerosol Properties and Their Relationship with the Heating Season in Urban Environments
Atmosphere 2021, 12(10), 1314; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101314 - 08 Oct 2021
Abstract
Black carbon (BC) aerosols have a considerable impact on humans because they not only cause environmental pollution and reduce visibility but also harm human health. During the heating season in northern China, a large amount of coal is burned for heating, producing a [...] Read more.
Black carbon (BC) aerosols have a considerable impact on humans because they not only cause environmental pollution and reduce visibility but also harm human health. During the heating season in northern China, a large amount of coal is burned for heating, producing a large amount of BC. There are few studies on BC properties during the heating season. In this paper, BC is measured optically, so it is referred to as equivalent black carbon (EBC). This paper investigated EBC properties in depth during the heating and nonheating seasons of a typical urban environment in China with two years of EBC measurements. The results show that: (1) EBC aerosol concentrations during the heating season were significantly higher than those during the nonheating season. (2) The main sources of EBC aerosols throughout the year are liquid sources. During the heating season, solid sources (coal and biomass combustion) are dominant. (3) The proportion of brown carbon (BrC) produced by biomass energy during the heating season is greater than that during the nonheating season. (4) The resulting backward trajectory indicates that a large portion of the high EBC aerosol concentration sources originate from northern and northwestern China. Our results reveal that the characteristics and sources of EBC in the urban environment of northern China vary widely, suggesting that different measures should be taken to reduce BC aerosol concentrations during heating and nonheating seasons. Full article
(This article belongs to the Special Issue Black Carbon Aerosol Monitoring and Its Radiative Forcing Effects)
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Article
Method of Source Identification Following an Accidental Release at an Unknown Location Using a Lagrangian Atmospheric Dispersion Model
Atmosphere 2021, 12(10), 1305; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101305 - 07 Oct 2021
Abstract
A computationally efficient source inversion algorithm was developed and applied with the Lagrangian atmospheric dispersion model DIPCOT. In the process of source location estimation by minimizing a correlation-based cost function, the algorithm uses only the values of the time-integrated concentrations at the monitoring [...] Read more.
A computationally efficient source inversion algorithm was developed and applied with the Lagrangian atmospheric dispersion model DIPCOT. In the process of source location estimation by minimizing a correlation-based cost function, the algorithm uses only the values of the time-integrated concentrations at the monitoring stations instead of all of the individual measurements in the full concentration-time series, resulting in a significant reduction in the number of integrations of the backward transport equations. Following the source location estimation the release start time, duration and emission rate are assessed. The developed algorithm was verified for the conditions of the ETEX-I (European Tracer Experiment—1st release). Using time-integrated measurements from all available stations, the distance between the estimated and true source location was 108 km. The estimated start time of the release was only about 1 h different from the true value, within the possible accuracy of estimate of this parameter. The estimated release duration was 21 h (the true value was 12 h). The estimated release rate was 4.28 g/s (the true value was 7.95 g/s). The estimated released mass almost perfectly fitted the true released mass (323.6 vs. 343.4 kg). It thus could be concluded that the developed algorithm is suitable for further integration in real-time decision support systems. Full article
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Article
Relationship between Drought and Precipitation Heterogeneity: An Analysis across Rain-Fed Agricultural Regions in Eastern Gansu, China
Atmosphere 2021, 12(10), 1274; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101274 - 29 Sep 2021
Abstract
Based on daily meteorological data from 55 meteorological stations in eastern Gansu from 1960 to 2017, the characteristics of the drought process and precipitation heterogeneity were analyzed, and the relationship between drought and precipitation heterogeneity was evaluated. Results showed that there were 1–3 [...] Read more.
Based on daily meteorological data from 55 meteorological stations in eastern Gansu from 1960 to 2017, the characteristics of the drought process and precipitation heterogeneity were analyzed, and the relationship between drought and precipitation heterogeneity was evaluated. Results showed that there were 1–3 drought processes in the study area every year. Drought processes in the eastern and north-central regions were more frequent than those in other regions. Droughts were mainly manifested as intra-seasonal droughts, especially across the spring and summer. PCD (Precipitation Concentration Degree, the concentration degree of the precipitation at a certain time) ranged from 0.2 to 0.7 in the area. PCD increased in spring and autumn but decreased in summer and winter for most regions from 1960 to 2017. PCP (Precipitation Concentration Period, the shortest time which the precipitation was concentrated in) was from late April to early May in spring, mid-to-late July in summer, mid-September in autumn, and late January in winter. In the last 58 years, PCP has remained consistent in most regions, varying by approximately 10 days. In addition to insignificant changes in winter, the days with light and moderate rain presented a declining trend, especially in summer and autumn. The larger the PCD, the fewer the days with light and moderate rain, and the stronger the drought intensity. However, in the east-central region, the larger the PCD in autumn, the weaker was the drought intensity. This difference is related to the PCP and the evapotranspiration. Additionally, the later the PCP, the stronger was the drought intensity, particularly in summer and autumn. When PCD was ≥0.5 in spring and ≥0.4 in summer, the PCP was after May and August in spring and summer, respectively. Droughts appeared in 28–56% of periods when seasonal precipitation was above normal. When PCD was ≥0.5 in autumn and PCP was in early and middle September, droughts appeared in 7% of periods when precipitation was above normal. Our results show that although less precipitation is the leading influencing factor of drought in the dry rain-fed agricultural areas, the influence of precipitation heterogeneity should be also considered for the prediction and diagnosis of seasonal drought. Full article
(This article belongs to the Special Issue Application of Homogenization Methods for Climate Records)
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Article
Decadal Variation of Atmospheric Rivers in Relation to North Atlantic Tripole SST Mode
Atmosphere 2021, 12(10), 1252; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101252 - 27 Sep 2021
Abstract
The North Atlantic tripole (NAT) is the leading mode of sea-surface temperature (SST) in the decadal time scale. Although the NAT is forced by North Atlantic oscillation (NAO), it also has an effect on the atmosphere; for example, the early winter tripole SST [...] Read more.
The North Atlantic tripole (NAT) is the leading mode of sea-surface temperature (SST) in the decadal time scale. Although the NAT is forced by North Atlantic oscillation (NAO), it also has an effect on the atmosphere; for example, the early winter tripole SST signal can influence storm tracks in March. As the NAT not only changes the baroclinicity of the lower layer but also modifies the moisture being released into the atmosphere, we surmise that the NAT has an impact on moisture transport and atmospheric rivers in the decadal time scale. Using ERA5 reanalysis data, the decadal variations in Atmospheric Rivers (ARs) in the North Atlantic in boral winter in relation to NAT phases were studied. During the positive NAT phase, the positive SST in the central and western North Atlantic increases the humidity and causes an anticyclonic wind response, which enhances the northeastward transport of moisture. As a result, ARs tend to be longer and transport more moisture toward northwestern Europe. This causes enhanced extreme rain in the UK and Norway. During the negative NAT phase, the positive SST anomalies in the south and east of the North Atlantic provide more moisture, induce a southward shift of the ARs and enhance extreme rain in the Iberian Peninsula. The Gulf Stream (GS) front is stronger during the negative NAT phase, increasing the frequency of the atmospheric front and enlarging the rain rate in ARs. Full article
(This article belongs to the Special Issue Atmospheric Rivers – Bridging Weather, Climate and Society)
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Article
Characteristics of Desert Precipitation in the UAE Derived from a Ceilometer Dataset
Atmosphere 2021, 12(10), 1245; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12101245 - 24 Sep 2021
Abstract
Understanding rainfall in arid and water-scarce regions is central to the efficient use of water resources in agriculture, irrigation, and domestic food security. This work presents a new dataset with which to study precipitation processes in arid regions, utilising two years (2018–2020) of [...] Read more.
Understanding rainfall in arid and water-scarce regions is central to the efficient use of water resources in agriculture, irrigation, and domestic food security. This work presents a new dataset with which to study precipitation processes in arid regions, utilising two years (2018–2020) of ceilometer observations made at Al Ain International Airport in the desert region of Al Ain, United Arab Emirates (UAE), where the annual rainfall is 76 mm. Ceilometer data provide a novel method by which to study both the evolution of water droplets from the cloud base down to the surface and the local circumstances required for rain to successfully reach the surface. In this work, we explore how successful precipitation depends on the initial size of the droplets and the thermodynamic profile below the cloud. For 64 of the 105 rain events, the droplet diameters ranged from 0.60 to 3.75 mm, with a mean of 1.84 mm. We find that smaller droplets, higher cloud bases, reduced cloud depths, and colder cloud bases all act to prevent successful precipitation, instead yielding virga (28 out of the 105 rain generating events). We identify how these multiple regional factors combine—specifically, we identify clouds deeper than 2.9 km, droplet diameters greater than 2 mm, and a midpoint below-cloud RH profile greater than 50%—to give successful rainfall, which may ultimately lead to more efficient rainfall enhancing measures, such as cloud seeding. Full article
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Article
Chemical Composition and Source Apportionment of Total Suspended Particulate in the Central Himalayan Region
Atmosphere 2021, 12(9), 1228; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091228 - 19 Sep 2021
Abstract
The present study analyzes data from total suspended particulate (TSP) samples collected during 3 years (2005–2008) at Nainital, central Himalayas, India and analyzed for carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)) and inorganic species, focusing on the assessment of primary and [...] Read more.
The present study analyzes data from total suspended particulate (TSP) samples collected during 3 years (2005–2008) at Nainital, central Himalayas, India and analyzed for carbonaceous aerosols (organic carbon (OC) and elemental carbon (EC)) and inorganic species, focusing on the assessment of primary and secondary organic carbon contributions (POC, SOC, respectively) and on source apportionment by positive matrix factorization (PMF). An average TSP concentration of 69.6 ± 51.8 µg m−3 was found, exhibiting a pre-monsoon (March–May) maximum (92.9 ± 48.5 µg m−3) due to dust transport and forest fires and a monsoon (June–August) minimum due to atmospheric washout, while carbonaceous aerosols and inorganic species expressed a similar seasonality. The mean OC/EC ratio (8.0 ± 3.3) and the good correlations between OC, EC, and nss-K+ suggested that biomass burning (BB) was one of the major contributing factors to aerosols in Nainital. Using the EC tracer method, along with several approaches for the determination of the (OC/EC)pri ratio, the estimated SOC component accounted for ~25% (19.3–29.7%). Furthermore, TSP source apportionment via PMF allowed for a better understanding of the aerosol sources in the Central Himalayan region. The key aerosol sources over Nainital were BB (27%), secondary sulfate (20%), secondary nitrate (9%), mineral dust (34%), and long-range transported mixed marine aerosol (10%). The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) analyses were also used to identify the probable regional source areas of resolved aerosol sources. The main source regions for aerosols in Nainital were the plains in northwest India and Pakistan, polluted cities like Delhi, the Thar Desert, and the Arabian Sea area. The outcomes of the present study are expected to elucidate the atmospheric chemistry, emission source origins, and transport pathways of aerosols over the central Himalayan region. Full article
(This article belongs to the Special Issue Aerosol Observations at High Altitude Stations)
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Article
Temporal Variability and Predictability of Intense Cyclones in the Western and Eastern Mediterranean
Atmosphere 2021, 12(9), 1218; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091218 - 17 Sep 2021
Abstract
Our understanding of the time variability of intense cyclones in the Mediterranean region is still lacking despite its importance for the long-term forecast of climate anomalies. This study examines the month-to-month variability and predictability of cyclones, the intensity of which exceeded the 75th [...] Read more.
Our understanding of the time variability of intense cyclones in the Mediterranean region is still lacking despite its importance for the long-term forecast of climate anomalies. This study examines the month-to-month variability and predictability of cyclones, the intensity of which exceeded the 75th percentile (intense cyclones) and the 95th percentile (extreme cyclones), over the Western and Eastern Mediterranean. The locations of cyclones were obtained by applying the method of M. Yu. Bardin on the 6-hourly 1000 hPa geopotential height data from the NCEP/NCAR reanalysis for the period 1951–2017 (67 years). It was shown that annual frequencies of cyclones were higher in the Western Mediterranean due to the contribution of spring and autumn; monthly averages were higher in the Eastern Mediterranean in December/January–March for intense/extreme cyclones. In the context of global warming, no linear trends significant at the 90% confidence level were found in the variability of intense and extreme cyclones, except for a positive trend in autumn extreme cyclones over the Eastern Mediterranean. The time series of cyclones in both parts of the Mediterranean were characterized by a pronounced interannual variability with a noticeable decadal modulation. According to spectral analysis, these interannual periods were multiples of 2–3 years corresponding to the main global teleconnection patterns. Seasonally, the most energy was concentrated in winter spectra; spring and autumn spectra had lower comparable magnitudes. The correlation analysis between the frequency of cyclones and the indices of the main atmospheric patterns showed that the main synchronous patterns for intense and extreme Mediterranean cyclones in September–April were the Mediterranean Oscillation (with the opposite signs for the Western and Eastern Mediterranean), Scandinavia pattern (positive correlation), and East Atlantic Oscillation (negative correlation). Additional important synchronous teleconnection patterns for some months were the Arctic Oscillation and East Atlantic/West Russia pattern for the Western Mediterranean, and the Polar/Eurasia pattern and Tropical Northern Hemisphere pattern for the Eastern Mediterranean. The outcome of this paper was the use of an artificial neural network model with inputs of global teleconnection indices both in the atmosphere and ocean to describe the temporal variability of the frequency of intense cyclones in the Western and Eastern Mediterranean. The predictability of intense cyclones was shown with the possibility of forecasts with a lead time of 0, 2, 4, and 6 months for the Western Mediterranean in October, January, February, April, and May, and for the Eastern Mediterranean in January, February, March, April, and May. One of the applications of this model may be in forecasting the evolution of the monthly frequency of cyclones with a lead time of 2 to 6 months. Full article
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Article
Improving Ensemble Volcanic Ash Forecasts by Direct Insertion of Satellite Data and Ensemble Filtering
Atmosphere 2021, 12(9), 1215; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091215 - 17 Sep 2021
Abstract
Improved quantitative forecasts of volcanic ash are in great demand by the aviation industry to enable better risk management during disruptive volcanic eruption events. However, poor knowledge of volcanic source parameters and other dispersion and transport modelling uncertainties, such as those due to [...] Read more.
Improved quantitative forecasts of volcanic ash are in great demand by the aviation industry to enable better risk management during disruptive volcanic eruption events. However, poor knowledge of volcanic source parameters and other dispersion and transport modelling uncertainties, such as those due to errors in numerical weather prediction fields, make this problem very challenging. Nonetheless, satellite-based algorithms that retrieve ash properties, such as mass load, effective radius, and cloud top height, combined with inverse modelling techniques, such as ensemble filtering, can significantly ameliorate these problems. The satellite-retrieved data can be used to better constrain the volcanic source parameters, but they can also be used to avoid the description of the volcanic source altogether by direct insertion into the forecasting model. In this study we investigate the utility of the direct insertion approach when employed within an ensemble filtering framework. Ensemble members are formed by initializing dispersion models with data from different timesteps, different values of cloud top height, thickness, and NWP ensemble members. This large ensemble is then filtered with respect to observations to produce a refined forecast. We apply this approach to 14 different eruption case studies in the tropical atmosphere. We demonstrate that the direct insertion of data improves model forecast skill, particularly when it is used in a hybrid ensemble in which some ensemble members are initialized from the volcanic source. Moreover, good forecast skill can be obtained even when detailed satellite retrievals are not available, which is frequently the case for volcanic eruptions in the tropics. Full article
(This article belongs to the Special Issue Data-Driven Methods in Atmospheric Dispersion Modelling)
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Article
Structure of the Pacific Walker Circulation Depicted by the Reanalysis and CMIP6
Atmosphere 2021, 12(9), 1219; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091219 - 17 Sep 2021
Abstract
The Pacific Walker circulation (PWC) is one of the most important components of large-scale tropical atmospheric circulations. The PWC and its influences have been studied extensively by numerical models and reanalysis. The newly released ERA5 and NCEP2 are the most widely used reanalysis [...] Read more.
The Pacific Walker circulation (PWC) is one of the most important components of large-scale tropical atmospheric circulations. The PWC and its influences have been studied extensively by numerical models and reanalysis. The newly released ERA5 and NCEP2 are the most widely used reanalysis datasets and serve as benchmarks for evaluation of model simulations. If the results of these datasets differ significantly, this could lead to a bias in projected long-term climate knowledge. For better understanding of future climate change, it is necessary to evaluate PWC reanalysis productions. As a result, we compared the PWC structures between the ERA5 and NCEP2 datasets from month to seasonal time scales. We used the zonal mass streamfunction (ZMS) over the equatorial Pacific to indicate the strength of the PWC. The PWC’s average monthly or seasonal cycle peaks around July. From February to June, the NCEP2 shows a higher PWC intensity, whereas the ERA5 shows greater intensity from July to December. The circulation center in the NCEP2 is generally stronger and wider than in the ERA5. The ERA5, however, revealed that the PWC’s west edge (zero line of ZMS over the western Pacific) had moved 10 degrees westward in comparison to the NCEP2. In addition, we compared the PWC mean state in the reanalysis and CMIP6 models; the mean state vertical structures of the tropical PWC in the CMIP6 multi-model ensemble (MME) are similar to those of the reanalyses in structure but weaker and wider than in the two reanalysis datasets. The PWC is broader in CMIP6, and the western boundary is 7 and 17 degrees farther west than in the ERA5 and NCEP2, respectively. This study suggests that, when using reanalysis datasets to evaluate PWC structural changes in intensity and western edge, extreme caution should be exercised. Full article
(This article belongs to the Special Issue ENSO: Dynamics, Predictability, Modelling and Teleconnection)
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Article
Real-Time Low-Cost Personal Monitoring for Exposure to PM2.5 among Asthmatic Children: Opportunities and Challenges
Atmosphere 2021, 12(9), 1192; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091192 - 15 Sep 2021
Abstract
This study aims to evaluate the accuracy and effectiveness of real-time personal monitoring of exposure to PM concentrations using low-cost sensors, in comparison to conventional data collection method based on fixed stations. PM2.5 data were measured every 5 min using a low-cost [...] Read more.
This study aims to evaluate the accuracy and effectiveness of real-time personal monitoring of exposure to PM concentrations using low-cost sensors, in comparison to conventional data collection method based on fixed stations. PM2.5 data were measured every 5 min using a low-cost sensor attached to a bag carried by 47 asthmatic children living in the Seoul Metropolitan area between November 2019 and March 2020, along with the real-time GPS location, temperature, and humidity. The mobile sensor data were then matched with station-based hourly PM2.5 data using the time and location. Despite some uncertainty and inaccuracy of the sensor data, similar temporal patterns were found between the two sources of PM2.5 data on an aggregate level. However, average PM2.5 concentrations via personal monitoring tended to be lower than those from the fixed stations, particularly when the subjects were indoors, during nighttime, and located farther from the fixed station. On an individual level, a substantial discrepancy is observed between the two PM2.5 data sources while staying indoors. This study provides guidance to policymakers and researchers on improving the feasibility of personal monitoring via low-cost mobile sensors as an alternative or supplement to the conventional station-based monitoring. Full article
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Article
Winter Air Pollution and Genotoxic Effects in Children Living in a Highly Polluted Urban Area
Atmosphere 2021, 12(9), 1191; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091191 - 15 Sep 2021
Abstract
Air pollutants, especially PM, have been found to determine various effects on human health, including genotoxic effects. The aim of this study was to assess DNA damage with micronuclei (MN) and comet tests on buccal cells of 6–8 years old children living in [...] Read more.
Air pollutants, especially PM, have been found to determine various effects on human health, including genotoxic effects. The aim of this study was to assess DNA damage with micronuclei (MN) and comet tests on buccal cells of 6–8 years old children living in an area with high air pollution. Both tests were repeated in the same children in two consecutive winters to compare the levels of DNA damage under different pollution conditions. A complete data set including lifestyle, air pollutants levels and biological sampling was available for 180 children in the two winters. A high mean MN frequency was found in both seasons, with higher value in the first (0.51 ± 0.59) than the second winter (0.40 ± 0.52), whereas DNA damage measured with comet test showed higher damage in the second versus the first winter (visual score 208.8 ± 67.1 vs. 173.2 ± 50.8). The associations between air pollutant levels (CO, NO2, SO2, benzene, O3, PM10, and PM2.5; PM0.5 and PAHs) and DNA damage were investigated at different lag times, and mainly, no significant association was found. This study on repeated measure of MN frequency and DNA damage in children’s buccal did not show an association with various air pollutants evaluated in an area with high levels of air pollution. Full article
(This article belongs to the Special Issue Outdoor Air Pollution and Human Health)
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Article
Flux–Profile Relationships in the Stable Boundary Layer—A Critical Discussion
Atmosphere 2021, 12(9), 1197; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091197 - 15 Sep 2021
Abstract
Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. [...] Read more.
Flux–profile relationships are crucial for parametrizing surface fluxes of momentum and heat, that are of central relevance for applications such as climate modelling and weather forecast. Nevertheless, their functional forms are still under discussion, and a generally accepted formulation does not exist yet. We reviewed the four main formulations proposed in the literature so far and assessed how they affect the theoretical behaviour of the kinematic heat flux (H0) and the temperature scale (T*) in the stable boundary layer, as well as their consequences on the existence of critical values for both the gradient and the flux Richardson numbers. None of them turned out to be fully consistent with the literature published so far, with two of them leading to very unreliable expressions for both H0 and T*. All considered, a convincing description of flux–profile relationships still needs to be found and seems to represents a considerable challenge. Full article
(This article belongs to the Special Issue The Stable Boundary Layer: Observations and Modeling)
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Article
Exercise under Exposure to Air Pollution and Spirometry in Healthy Adults with and without Allergy
Atmosphere 2021, 12(9), 1168; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091168 - 11 Sep 2021
Abstract
Ambient air pollution is a major environmental threat to human health. The acute effects of exposure to ambient air pollution during physical exercise may depend on allergy status. The aim of the study was to assess the acute respiratory responses to air pollution [...] Read more.
Ambient air pollution is a major environmental threat to human health. The acute effects of exposure to ambient air pollution during physical exercise may depend on allergy status. The aim of the study was to assess the acute respiratory responses to air pollution exposure during physical training in young adults with and without allergies. The studied group included 71 healthy young adults (n = 16 with allergy and n = 55 without allergy). Students completed two indoor physical training trials lasting 45–60 min: when air pollutants concentrations were high (exposure trial) and low (control trial). During each trial, we monitored outdoor and indoor environmental conditions. Participants performed spirometry at baseline and directly after the exercise. Exercise during exposure trials led to a small decrease in the percentage of predicted forced expiratory volume in 1 s (FEV1 ref). Only during the control trials did the FEV1/forced vital capacity quotient (FEV1/FVC) statistically significantly increase. Moreover, just in the allergy group, there were statistically significant negative correlations between post-exercise FEV1/FVC change and 3 h average outdoor particulate matter with aerodynamic diameter <10 µm (PM10) and nitrogen dioxide (NO2) concentrations (PM10: r = −0.54, p = 0.02, NO2: r = −0.60, p = 0.02). In young and healthy adults, sports training under exposure to high levels of ambient air pollutants leads to a small decrease in FEV1. The allergy might be a modifying factor in the respiratory responses to air pollution. Post-exercise decrease in FEV1/FVC was related to pre-exercise 3 h averages of PM10 and NO2 only in people with ever-diagnosed upper-respiratory allergy. Full article
(This article belongs to the Special Issue Outdoor Air Pollution and Human Health)
Article
Tropical Cyclone Formation within Strong Northeasterly Environments in the South China Sea
Atmosphere 2021, 12(9), 1147; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091147 - 05 Sep 2021
Abstract
In the South China Sea (SCS), 17% of tropical cyclones (TCs) formed in the late season (November−January) were associated with a strong northeasterly monsoon. This study explores the effects of northeasterly strength on TC formation over the SCS. The Weather Research and Forecasting [...] Read more.
In the South China Sea (SCS), 17% of tropical cyclones (TCs) formed in the late season (November−January) were associated with a strong northeasterly monsoon. This study explores the effects of northeasterly strength on TC formation over the SCS. The Weather Research and Forecasting (WRF) model is used to simulate the disturbances that develop into TCs (formation cases) and those that do not (non-formation cases). Two formation (29W on 18 November 2001 and Vamei on 26 December 2001) and two non-formation (30 December 2002 and 9 January 2003) cases are simulated. To address the importance of upstream low-level northeasterly strength to TC formation, two types of sensitivity experiments are performed: formation cases with increased northeasterly flow and non-formation cases with decreased northeasterly flow. If the strength of the northeasterly is increased for the formation case, the stronger cold advection reduces the convective instability around the disturbance center, leading to the weakening of the simulated disturbance. If the strength of the northeasterly is decreased for the non-formation case, the simulated disturbance can develop further into a TC. In summary, strength of the upstream low-level northeasterly flow does affect the environmental conditions around the disturbance center, resulting in the change of TC formation probability over the SCS in the late season. Full article
(This article belongs to the Special Issue Asia-Pacific Region: Monsoons and Typhoons)
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Article
Large Eddy Simulations of Turbulent and Buoyant Flows in Urban and Complex Terrain Areas Using the Aeolus Model
Atmosphere 2021, 12(9), 1107; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091107 - 27 Aug 2021
Abstract
Fast and accurate predictions of the flow and transport of materials in urban and complex terrain areas are challenging because of the heterogeneity of buildings and land features of different shapes and sizes connected by canyons and channels, which results in complex patterns [...] Read more.
Fast and accurate predictions of the flow and transport of materials in urban and complex terrain areas are challenging because of the heterogeneity of buildings and land features of different shapes and sizes connected by canyons and channels, which results in complex patterns of turbulence that can enhance material concentrations in certain regions. To address this challenge, we have developed an efficient three-dimensional computational fluid dynamics (CFD) code called Aeolus that is based on first principles for predicting transport and dispersion of materials in complex terrain and urban areas. The model can be run in a very efficient Reynolds average Navier–Stokes (RANS) mode or a detailed large eddy simulation (LES) mode. The RANS version of Aeolus was previously validated against field data for tracer gas and radiological dispersal releases. As a part of this work, we have validated the Aeolus model in LES mode against two different sets of data: (1) turbulence quantities measured in complex terrain at Askervein Hill; and (2) wind and tracer data from the Joint Urban 2003 field campaign for urban topography. As a third set-up, we have applied Aeolus to simulate cloud rise dynamics for buoyant plumes from high-temperature explosions. For all three cases, Aeolus LES predictions compare well to observations and other models. These results indicate that Aeolus LES can be used to accurately simulate turbulent flow and transport for a wide range of applications and scales. Full article
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Article
Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece
Atmosphere 2021, 12(9), 1100; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091100 - 25 Aug 2021
Cited by 1
Abstract
To date, due to climate change, heatwaves are more frequent, with greater intensity and duration resulting in deleterious impacts on human health. To be able to manage heatwaves and quantify the impacts on human health, it is crucial to define them and implement [...] Read more.
To date, due to climate change, heatwaves are more frequent, with greater intensity and duration resulting in deleterious impacts on human health. To be able to manage heatwaves and quantify the impacts on human health, it is crucial to define them and implement policy preventive measures. However, heatwaves are relative to the climate of a location: The same meteorological conditions can constitute a heatwave in one place but not in another. Due to different climatic conditions, social characteristics, and adaptation, heatwaves should be defined on a local scale, which poses difficulties when it comes to comparison of different definitions. The aim of the present study is to define heatwaves, implementing robust statistical analysis for three different indicators (temperature, physiological equivalent temperature (PET), and universal thermal climate index (UTCI)) for three causes of mortality (i.e., cardiological and respiratory mortality and cardiorespiratory mortality) using Attica (Greece) as a case study. Our results define a heatwave for Attica as a period of at least 3 days when the mean temperature is higher than the 97.5th percentile. Afterwards, we encapsulate the harvesting effect by implementing robust statistical analysis, using the Superposed Epoch analysis. Consequently, quantifying heatwaves is crucial so as to create early warning systems and prevent avoidable mortality. Full article
(This article belongs to the Section Biometeorology)
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Article
Impact of Soil Moisture Data Assimilation on Analysis and Medium-Range Forecasts in an Operational Global Data Assimilation and Prediction System
Atmosphere 2021, 12(9), 1089; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12091089 - 24 Aug 2021
Abstract
Accurate initial soil moisture conditions are essential for numerical weather prediction models, because they play a major role in land–atmosphere interactions. This study constructed a soil moisture data assimilation system and evaluated its impacts on the Global Data Assimilation and Prediction System based [...] Read more.
Accurate initial soil moisture conditions are essential for numerical weather prediction models, because they play a major role in land–atmosphere interactions. This study constructed a soil moisture data assimilation system and evaluated its impacts on the Global Data Assimilation and Prediction System based on the Korea Integrated Model (GDAPS-KIM) to improve its weather forecast skill. Soil moisture data retrieved from the Advanced Scatterometer (ASCAT) onboard the Meteorological Operational Satellite was assimilated into GDAPS-KIM using the ensemble Kalman filter method, and its impacts were evaluated for the 2019 boreal summer period. Our results indicated that the soil moisture data assimilation improved the agreement of the observations with the initial conditions of GDAPS-KIM. This led to a statistically significant improvement in the accuracy of the initial fields. A comparison of a five-day forecast against an ERA5 reanalysis and in situ observations revealed a reduction in the dry and warm biases of GDAPS-KIM over the surface and in the lower- and mid-level atmospheres. The temperature bias correction through the initialization of the soil moisture estimates from the data assimilation system was shown in the five-day weather forecast (root mean squared errors reduction of the temperature at 850 hPa by approximately 5% in East Asia). Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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Article
Adaptive Crop Management under Climate Uncertainty: Changing the Game for Sustainable Water Use
Atmosphere 2021, 12(8), 1080; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081080 - 23 Aug 2021
Abstract
Water supplies are projected to become increasingly scarce, driving farmers, energy producers, and urban dwellers towards an urgent and emerging need to improve the effectiveness and the efficiency of water use. Given that agricultural water use is the largest water consumer throughout the [...] Read more.
Water supplies are projected to become increasingly scarce, driving farmers, energy producers, and urban dwellers towards an urgent and emerging need to improve the effectiveness and the efficiency of water use. Given that agricultural water use is the largest water consumer throughout the U.S. Southwest, this study sought to answer two specific research questions: (1) How does water consumption vary by crop type on a metropolitan spatial scale? (2) What is the impact of drought on agricultural water consumption? To answer the above research questions, 92 Landsat images were acquired to generate fine-resolution daily evapotranspiration (ET) maps at 30 m spatial resolution for both dry and wet years (a total of 1095 ET maps), and major crop types were identified for the Phoenix Active Management Area. The study area has a subtropical desert climate and relies almost completely on irrigation for farming. Results suggest that there are some factors that farmers and water managers can control. During dry years, crops of all types use more water. Practices that can offset this higher water use include double or multiple cropping practice, drought tolerant crop selection, and optimizing the total farmed area. Double and multiple cropping practices result in water savings because soil moisture is retained from one planting to another. Further water savings occur when drought tolerant crop types are selected, especially in dry years. Finally, disproportionately large area coverage of high water consuming crops can be balanced and/or reduced or replaced with more water efficient crops. This study provides strong evidence that water savings can be achieved through policies that create incentives for adopting smart cropping strategies, thus providing important guidelines for sustainable agriculture management and climate adaptation to improve future food security. Full article
(This article belongs to the Special Issue Remote Sensing and GIS Applications in Urban Climate Research)
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Article
30 Years of Air Quality Trends in Japan
Atmosphere 2021, 12(8), 1072; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081072 - 21 Aug 2021
Abstract
The aim of this paper is to obtain information that will contribute to measures and research needed to further improve the air quality in Japan. The trends and characteristics of air pollutant concentrations, especially PM2.5, ozone, and related substances, over the past [...] Read more.
The aim of this paper is to obtain information that will contribute to measures and research needed to further improve the air quality in Japan. The trends and characteristics of air pollutant concentrations, especially PM2.5, ozone, and related substances, over the past 30 years, are analyzed, and the relationships between concentrations and emissions are discussed quantitatively. We found that PM2.5 mass concentrations have decreased, with the largest reduction in elemental carbon (EC) as the PM2.5 component. The concentrations of organic carbon (OC) have not changed significantly compared to other components, suggesting that especially VOC emissions as precursors need to be reduced. In addition, the analysis of the differences in PM2.5 concentrations between the ambient and the roadside showed that further research on non-exhaust particles is needed. For NOx and SO2, there is a linear relationship between domestic anthropogenic emissions and atmospheric concentrations, indicating that emission control measures are directly effective in the reduction in concentrations. Also, recent air pollution episodes and the effect of reduced economic activity, as a consequence of COVID-19, on air pollution concentrations are summarized. Full article
(This article belongs to the Special Issue Air Pollution in Japan)
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Article
Fine-Resolution WRF Simulation of Stably Stratified Flows in Shallow Pre-Alpine Valleys: A Case Study of the KASCADE-2017 Campaign
Atmosphere 2021, 12(8), 1063; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081063 - 19 Aug 2021
Abstract
In an overall approach aiming at the development and qualification of various tools designed to diagnose and/or forecast the flows at the local scale in complex terrain, we qualified a numerical model based on the WRF platform and operated in a two-way nested [...] Read more.
In an overall approach aiming at the development and qualification of various tools designed to diagnose and/or forecast the flows at the local scale in complex terrain, we qualified a numerical model based on the WRF platform and operated in a two-way nested domain mode, down to a horizontal resolution of 111 m for the smallest domain. The area in question is the Cadarache valley (CV), in southeast France, which is surrounded by hills and valleys of various sizes. The CV dimensions (1 km wide and 100 m deep) favor the development of local flows greatly influenced by the diurnal cycle and are prone to thermal stratification, especially during stable conditions. This cycle was well documented due to permanent observations and dedicated field campaigns. These observations were used to evaluate the performance of the model on a specific day among the intensive observation periods carried out during the KASCADE-2017 campaign. The model reproduced the wind flow and its diurnal cycle well, notably at the local CV scale, which constitutes considerable progress with respect to the performances of previous WRF simulations conducted in this area with kilometric resolution, be it operational weather forecasts or dedicated studies conducted on specific days. The diurnal temperature range is underestimated however, together with the stratification intensity of the cold pool observed at night. Consequently, the slope drainage flows along the CV sidewalls are higher in the simulation than in the observations, and the resulting scalar fields (such as specific humidity) are less heterogeneous in the model than in the observations. Full article
(This article belongs to the Special Issue The Stable Boundary Layer: Observations and Modeling)
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Article
Extreme Translation Events of Atlantic Tropical Cyclones
Atmosphere 2021, 12(8), 1032; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081032 - 12 Aug 2021
Abstract
Changes in the translational speed of tropical cyclones (e.g., sluggish tropical cyclones) are associated with extreme precipitation and flash flooding. However, it is still unclear regarding the spatial and temporal variability of extreme tropical cyclone translation events in the North Atlantic and underlying [...] Read more.
Changes in the translational speed of tropical cyclones (e.g., sluggish tropical cyclones) are associated with extreme precipitation and flash flooding. However, it is still unclear regarding the spatial and temporal variability of extreme tropical cyclone translation events in the North Atlantic and underlying large-scale drivers. This work finds that the frequencies of extreme fast- and slow-translation events of Atlantic tropical cyclones exhibited a significant rising trend during 1980–2019. The extreme fast-translation events of Atlantic tropical cyclones are primarily located in the northern part of the North Atlantic, while the extreme slow-translation events are located more equatorward. There is a significant rising trend in the frequency of extreme slow-translation events over ocean with no trend over land. However, there is a significant rising trend in the frequency of extreme fast-translation events over ocean and over land. The extreme slow-translation events are associated with a strong high-pressure system in the continental United States (U.S.). By contrast, the extreme fast-translation events are related to a low-pressure system across most of the continental U.S. that leads to westerly steering flow that enhances tropical cyclone movement. This study suggests that it might be useful to separate tropical cyclone events into fast-moving and slow-moving groups when examining the translational speed of North Atlantic tropical cyclones, instead of examining regional or global mean translational speed. Full article
(This article belongs to the Special Issue Extreme Tropical Cyclones)
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Article
Characteristics of Enhanced Heatwaves over Tanzania and Scenario Projection in the 21st Century
Atmosphere 2021, 12(8), 1026; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081026 - 11 Aug 2021
Cited by 1
Abstract
Extreme hot temperature is dangerous to the bioeconomy, and would worsen with time. Ambient heatwaves accompanied by unusual droughts are major threats to poverty eradication in Tanzania. Due to sparsity of observation data and proper heatwave detection metrics, there has been a paucity [...] Read more.
Extreme hot temperature is dangerous to the bioeconomy, and would worsen with time. Ambient heatwaves accompanied by unusual droughts are major threats to poverty eradication in Tanzania. Due to sparsity of observation data and proper heatwave detection metrics, there has been a paucity of knowledge about heatwave events in Tanzania. In this study, the Heatwave Magnitude Index daily (HWMId) was adopted to quantitatively analyze heatwave characteristics throughout Tanzania at mid-21st century (2041–2070) and end of 21st century (2071–2100), relative to the reference period (1983–2012) using the CHIRTS-daily quasi-global high-resolution temperature dataset and climate simulations from a multi-modal ensemble of median scenarios (RCP4.5, from CORDEX-Africa). The results showed that moderate to super-extreme heatwaves occurred in Tanzania between 1983 and 2012, particularly in 1999, when ultra-extreme heatwaves (HWMId > 32) occurred in the Lake Victoria basin. It is projected that by mid-21st century, the upper category of HWMId would be hotter and longer, and would occur routinely in Tanzania. The spatial extent of all of the HWMId categories is projected to range from 34% to 73% by the end of the 21st century with a duration of 8 to 35 days, compared to 1 to 5 days during the reference period. These findings will contribute to increasing public awareness of the need for adaptation. Full article
(This article belongs to the Section Biometeorology)
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Article
On the Relationship of Cold Pool and Bulk Shear Magnitudes on Upscale Convective Growth in the Great Plains of the United States
Atmosphere 2021, 12(8), 1019; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081019 - 09 Aug 2021
Abstract
Upscale convective growth remains a poorly understood aspect of convective evolution, and numerical weather prediction models struggle to accurately depict convective morphology. To better understand some physical mechanisms encouraging upscale growth, 30 warm-season convective events from 2016 over the United States Great Plains [...] Read more.
Upscale convective growth remains a poorly understood aspect of convective evolution, and numerical weather prediction models struggle to accurately depict convective morphology. To better understand some physical mechanisms encouraging upscale growth, 30 warm-season convective events from 2016 over the United States Great Plains were simulated using the Weather Research and Forecasting (WRF) model to identify differences in upscale growth and non-upscale growth environments. Also, Bryan Cloud Model (CM1) sensitivity tests were completed using different thermodynamic environments and wind profiles to examine the impact on upscale growth. The WRF simulations indicated that cold pools are significantly stronger in cases that produce upscale convective growth within the first few hours following convective initiation compared to those without upscale growth. Conversely, vertical wind shear magnitude has no statistically significant relationship with either MCS or non-MCS events. This is further supported by the CM1 simulations, in which tests using the WRF MCS sounding developed a large convective system in all tests performed, including one which used the non-MCS kinematic profile. Likewise, the CM1 simulations of the non-upscale growth event did not produce an MCS, even when using the MCS kinematic profile. Overall, these results suggest that the near-storm and pre-convective thermodynamic environment may play a larger role than kinematics in determining upscale growth potential in the Great Plains. Full article
(This article belongs to the Section Meteorology)
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Article
The Impact of Smog Pollution on Audit Quality: Evidence from China
Atmosphere 2021, 12(8), 1015; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081015 - 07 Aug 2021
Cited by 1
Abstract
Audit quality usually refers to the quality that the auditing services accounting firm auditors provide to an enterprise in the form of an audit report. This study empirically analyzes the impact mechanism of smog pollution on audit quality, based on the data of [...] Read more.
Audit quality usually refers to the quality that the auditing services accounting firm auditors provide to an enterprise in the form of an audit report. This study empirically analyzes the impact mechanism of smog pollution on audit quality, based on the data of A-share listed companies in the Shanghai and Shenzhen Stock Exchanges during the period 2013 to 2017 and the air quality monitoring data released by the China National Environmental Monitoring Centre covering the period 2013 to 2018. First, the empirical results show that smog pollution can lead to a decline in audit quality. Second, audit time plays a partial mediating role in the relationship between smog pollution and audit quality. Further analysis indicates that the negative impact of smog pollution on audit quality and the intermediary role played by audit time are only significant in the sample of “top 10” accounting firms. Third, the enterprise′s internal control level positively moderates the mediating effect of audit time on smog pollution and audit quality. Full article
(This article belongs to the Special Issue Aerosol Pollution in Asia)
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Article
Air Quality in the Italian Northwestern Alps during Year 2020: Assessment of the COVID-19 «Lockdown Effect» from Multi-Technique Observations and Models
Atmosphere 2021, 12(8), 1006; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12081006 - 05 Aug 2021
Cited by 4
Abstract
The effect of COVID-19 confinement regulations on air quality in the northwestern Alps is assessed here based on measurements at five valley sites in different environmental contexts. Surface concentrations of nitrogen oxides (NO and NO2), ozone (O3), particulate matter [...] Read more.
The effect of COVID-19 confinement regulations on air quality in the northwestern Alps is assessed here based on measurements at five valley sites in different environmental contexts. Surface concentrations of nitrogen oxides (NO and NO2), ozone (O3), particulate matter (PM2.5 and PM10), together with a thorough microphysical (size), chemical, and optical (light absorption) aerosol characterisation, complemented by observations along the vertical column are considered. Even in the relatively pristine environment of the Alps, the «lockdown effect» is well discernible, both in the early confinement phase and in late 2020. The variations observed during the first confinement period in the city of Aosta (−61% NO, −43% NO2, +5% O3, +9% PM2.5, −12% PM10, relative to average 2015–2019 conditions) are attributed to the competing effects of air pollution lockdown-induced changes (−74%, −52%, +18%, −13%, −27%, relative to the counterfactual scenario for 2020 provided by a predictive statistical model trained on past measurements) and meteorology (+52%, +18%, −11%, +25%, +20%, relative to average conditions). These changes agree well with the ones obtained from a chemical transport model with modified emissions according to the restrictions. With regard to column-integrated quantities and vertical profiles, the NO2 column density decreases by >20% due to the lockdown, whereas tropospheric aerosols are mainly influenced by large-scale dynamics (transport of secondary particles from the Po basin and mineral dust from the Sahara desert and the Caspian Sea), except a shallow layer about 500 m thick close to the surface, possibly sensitive to curtailed emissions (especially exhaust and non-exhaust particles from road traffic and fugitive emissions from the industry). Full article
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Article
Environmental Factors Controlling the Precipitation in California
Atmosphere 2021, 12(8), 997; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080997 - 02 Aug 2021
Abstract
Using observational data covering 1948–2020, the environmental factors controlling the winter precipitation in California were investigated. Empirical orthogonal function (EOF) analysis was applied to identify the dominant climate regimes contributing to the precipitation. The first EOF mode described a consistent change, with 70.1% [...] Read more.
Using observational data covering 1948–2020, the environmental factors controlling the winter precipitation in California were investigated. Empirical orthogonal function (EOF) analysis was applied to identify the dominant climate regimes contributing to the precipitation. The first EOF mode described a consistent change, with 70.1% variance contribution, and the second mode exhibited a south–east dipole change, with 11.7% contribution. For EOF1, the relationship was positive between PC1(principal component) and SST (sea surface temperature) in the central Pacific Ocean, while it was negative with SST in the southeast Indian Ocean. The Pacific–North America mode, induced by the positive SST and precipitation in the central Pacific Ocean, leads to California being occupied by southwesterlies, which would transport warm and wet flow from the ocean, beneficial for precipitation. As for the negative relationship, California is controlled by biotrophically high pressure, representing part of the Rossby wave train induced by the positive SST in the Indian ocean, which is unfavorable for the precipitation. For EOF2, California is controlled by positive vorticity at the upper level, whereas at the lower level, there is positive vorticity to the south and negative vorticity to the north, the combination of which leads to the dipole mode change in the precipitation. Full article
(This article belongs to the Special Issue Tropical Ocean-Atmosphere Interaction and Climate Change)
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Article
Experimental Comparative Study between Conventional and Green Parking Lots: Analysis of Subsurface Thermal Behavior under Warm and Dry Summer Conditions
Atmosphere 2021, 12(8), 994; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080994 - 31 Jul 2021
Cited by 1
Abstract
Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal [...] Read more.
Green infrastructure has a role to play in climate change adaptation strategies in cities. Alternative urban spaces should be designed considering new requirements in terms of urban microclimate and thermal comfort. Pervious pavements such as green parking lots can contribute to this goal through solar evaporative cooling. However, the cooling benefits of such systems remain under debate during dry and warm periods. The aim of this study was to compare experimentally the thermal behavior of different parking lot types (PLTs) with vegetated urban soil. Four parking lots were instrumented, with temperature probes buried at different depths. Underground temperatures were measured during summer 2019, and the hottest days of the period were analyzed. Results show that the less mineral used in the surface coating, the less it warms up. The temperature difference at the upper layer can reach 10 °C between mineral and non-mineral PLTs. PLTs can be grouped into three types: (i) high surface temperature during daytime and nighttime, important heat transfer toward the sublayers, and low time shift (asphalt system); (ii) high (resp. low) surface temperature during daytime (resp. nighttime), weak heat transfer toward the sublayers, and important time shift (paved stone system); and (iii) low surface temperature during daytime and nighttime, weak heat transfer toward the sublayers, and important time shift (vegetation and substrate system, wood chips system, vegetated urban soil). The results of this study underline that pervious pavements demonstrate thermal benefits under warm and dry summer conditions compared to conventional parking lot solutions. The results also indicate that the hygrothermal properties of urban materials are crucial for urban heat island mitigation. Full article
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Article
A CFD Approach for Risk Assessment Based on Airborne Pathogen Transmission
Atmosphere 2021, 12(8), 986; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080986 - 30 Jul 2021
Cited by 2
Abstract
The outbreak of COVID-19 necessitates developing reliable tools to derive safety measures, including safe social distance and minimum exposure time under different circumstances. Transient Eulerian–Lagrangian computational fluid dynamics (CFD) models have emerged as a viably fast and economical option. Nonetheless, these CFD models [...] Read more.
The outbreak of COVID-19 necessitates developing reliable tools to derive safety measures, including safe social distance and minimum exposure time under different circumstances. Transient Eulerian–Lagrangian computational fluid dynamics (CFD) models have emerged as a viably fast and economical option. Nonetheless, these CFD models resolve the instantaneous distribution of droplets inside a computational domain, making them incapable of directly being used to assess the risk of infection as it depends on the total accumulated dosage of infecting viruses received by a new host within an exposure time. This study proposes a novel risk assessment model (RAM) to predict the temporal and spatial accumulative concentration of infectious exhaled droplets based on the bio-source’s exhalation profile and droplet distribution using the CFD results of respiratory events in various environmental conditions. Unlike the traditional approach in the bulk movement assessment of droplets’ outreach in a domain, every single droplet is traced inside the domain at each time step, and the total number of droplets passing through any arbitrary position of the domain is determined using a computational code. The performance of RAM is investigated for a series of case studies against various respiratory events where the horizontal and the lateral spread of risky zones are shown to temporarily vary rather than being fixed in space. The sensitivity of risky zones to ambient temperature and relative humidity was also addressed for sample cough and sneeze cases. This implies that the RAM provides crucial information required for defining safety measures such as safety distances or minimum exposure times in different environments. Full article
(This article belongs to the Special Issue Transport Phenomena in the Atmospheric Boundary Layer)
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Article
Spatial and Temporal Characteristics of Rainfall Anomalies in 1961–2010 in the Yangtze River Basin, China
Atmosphere 2021, 12(8), 960; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080960 - 27 Jul 2021
Abstract
Understanding rainfall anomalies and their relationship with floods in the Yangtze River Basin (YRB) is essential for evaluating flood disasters, which have a great impact on the development of agriculture and the economy. On the basis of daily rainfall data from 1961 to [...] Read more.
Understanding rainfall anomalies and their relationship with floods in the Yangtze River Basin (YRB) is essential for evaluating flood disasters, which have a great impact on the development of agriculture and the economy. On the basis of daily rainfall data from 1961 to 2010 from 178 meteorological stations, the temporal and spatial characteristics of rainfall anomalies in the YRB were studied on an annual scale, seasonal scale, and monthly scale. The annual rainfall of the YRB showed a generally increasing trend from 1961 to 2010 (14.22 mm/10 a). By means of the Bernaola–Galvan abrupt change test and Redfit spectrum analysis, it was found that the annual average rainfall increased abruptly after 1979 and had a cycle of 2–3 years. On the seasonal scale, the rainfall in spring and autumn showed a gradually decreasing trend, especially in September, while it showed a significant increasing trend in summer and winter in the YRB. As for the monthly scale, the rainfall in the rainy season from June to July presented a clear increasing trend during the study period, which greatly enhanced the probability of floods in the YRB. Additionally, through the analysis of the spatial distribution characteristics of rainfall in the entire YRB from 1961 to 2010, it was observed that the annual rainfall amount in the YRB presented an “increase–decrease–increase” tendency from east to west, accompanied by a rain belt that continuously moved from west to east. Moreover, the rainfall characteristics in flood years were summarized, and the results revealed that the years with rainfall anomalies were more likely to have flood disasters. However, anomalies alone would not result in big floods; the spatially and temporally inhomogeneous rainfall distribution might be the primary reason for flood disasters in the entire YRB. Full article
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Article
Assessment of Low-Cost Particulate Matter Sensor Systems against Optical and Gravimetric Methods in a Field Co-Location in Norway
Atmosphere 2021, 12(8), 961; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080961 - 27 Jul 2021
Cited by 1
Abstract
The increased availability of commercially-available low-cost air quality sensors combined with increased interest in their use by citizen scientists, community groups, and professionals is resulting in rapid adoption, despite data quality concerns. We have characterized three out-the-box PM sensor systems under different environmental [...] Read more.
The increased availability of commercially-available low-cost air quality sensors combined with increased interest in their use by citizen scientists, community groups, and professionals is resulting in rapid adoption, despite data quality concerns. We have characterized three out-the-box PM sensor systems under different environmental conditions, using field colocation against reference equipment. The sensor systems integrate Plantower 5003, Sensirion SPS30 and Alphasense OCP-N3 PM sensors. The first two use photometry as a measuring technique, while the third one is an optical particle counter. For the performance evaluation, we co-located 3 units of each manufacturer and compared the results against optical (FIDAS) and gravimetric (KFG) methods for a period of 7 weeks (28 August to 19 October 2020). During the period from 2nd and 5th October, unusually high PM concentrations were observed due to a long-range transport episode. The results show that the highest correlations between the sensor systems and the optical reference are observed for PM1, with coefficients of determination above 0.9, followed by PM2.5. All the sensor units struggle to correctly measure PM10, and the coefficients of determination vary between 0.45 and 0.64. This behavior is also corroborated when using the gravimetric method, where correlations are significantly higher for PM2.5 than for PM10, especially for the sensor systems based on photometry. During the long range transport event the performance of the photometric sensors was heavily affected, and PM10 was largely underestimated. The sensor systems evaluated in this study had good agreement with the reference instrumentation for PM1 and PM2.5; however, they struggled to correctly measure PM10. The sensors also showed a decrease in accuracy when the ambient size distribution was different from the one for which the manufacturer had calibrated the sensor, and during weather conditions with high relative humidity. When interpreting and communicating air quality data measured using low-cost sensor systems, it is important to consider such limitations in order not to risk misinterpretation of the resulting data. Full article
(This article belongs to the Special Issue The Future of Air Quality Monitoring)
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Article
Turbulent Momentum Flux Behavior above a Fire Front in an Open-Canopied Forest
Atmosphere 2021, 12(8), 956; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080956 - 24 Jul 2021
Abstract
Atmospheric turbulent circulations in the vicinity of wildland fire fronts play an important role in the transfer of momentum into and out of combustion zones, which in turn can potentially affect the behavior and spread of wildland fires. The vertical turbulent transfer of [...] Read more.
Atmospheric turbulent circulations in the vicinity of wildland fire fronts play an important role in the transfer of momentum into and out of combustion zones, which in turn can potentially affect the behavior and spread of wildland fires. The vertical turbulent transfer of momentum is accomplished via individual sweep, ejection, outward interaction, and inward interaction events, collectively known as sweep-ejection dynamics. This study examined the sweep-ejection dynamics that occurred before, during, and after the passage of a surface fire front during a prescribed fire experiment conducted in an open-canopied forest in the New Jersey Pine Barrens. High-frequency (10 Hz), tower-based, sonic anemometer measurements of horizontal and vertical wind velocity components in the vicinity of the fire front were used to assess the relative frequencies of occurrence of the different types of momentum-flux events, their contributions to the overall momentum fluxes, and their periodicity patterns. The observational results suggest that the presence of surface fire fronts in open-canopied forests can substantially change the sweep-ejection dynamics that typically occur when fires are not present. In particular, sweep events resulting in the downward transport of high horizontal momentum air from above were found to be more prominent during fire-front-passage periods. Full article
(This article belongs to the Section Biometeorology)
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Article
Expected Health Effects of Reduced Air Pollution from COVID-19 Social Distancing
Atmosphere 2021, 12(8), 951; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080951 - 23 Jul 2021
Cited by 1
Abstract
The COVID-19 pandemic resulted in stay-at-home policies and other social distancing behaviors in the United States in spring of 2020. This paper examines the impact that these actions had on emissions and expected health effects through reduced personal vehicle travel and electricity consumption. [...] Read more.
The COVID-19 pandemic resulted in stay-at-home policies and other social distancing behaviors in the United States in spring of 2020. This paper examines the impact that these actions had on emissions and expected health effects through reduced personal vehicle travel and electricity consumption. Using daily cell phone mobility data for each U.S. county, we find that vehicle travel dropped about 40% by mid-April across the nation. States that imposed stay-at-home policies before March 28 decreased travel slightly more than other states, but travel in all states decreased significantly. Using data on hourly electricity consumption by electricity region (e.g., balancing authority), we find that electricity consumption fell about 6% on average by mid-April with substantial heterogeneity. Given these decreases in travel and electricity use, we estimate the county-level expected improvements in air quality, and, therefore, expected declines in mortality. Overall, we estimate that, for a month of social distancing, the expected premature deaths due to air pollution from personal vehicle travel and electricity consumption declined by approximately 360 deaths, or about 25% of the baseline 1500 deaths. In addition, we estimate that CO2 emissions from these sources fell by 46 million metric tons (a reduction of approximately 19%) over the same time frame. Full article
(This article belongs to the Special Issue Human Health, Climate Change, and Ambient Air Pollution)
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Article
Spatial Distribution of Black Carbon Concentrations in the Atmosphere of the North Atlantic and the European Sector of the Arctic Ocean
Atmosphere 2021, 12(8), 949; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080949 - 23 Jul 2021
Abstract
We discuss the measurements of black carbon concentrations in the composition of atmospheric aerosol over the seas of the North Atlantic and European sector of the Arctic Ocean (21 expeditions in 2007–2020). The black carbon concentrations were measured by an aethalometer and filter [...] Read more.
We discuss the measurements of black carbon concentrations in the composition of atmospheric aerosol over the seas of the North Atlantic and European sector of the Arctic Ocean (21 expeditions in 2007–2020). The black carbon concentrations were measured by an aethalometer and filter method. The comparison of the two variants of the measurements of the black carbon concentrations showed that the data acceptably agreed and can be used jointly. It is noted that the spatial distribution of black carbon over the ocean is formed under the influence of outflows of air masses from the direction of continents, where the main sources of emission of absorbing aerosol are concentrated. We analyzed the statistical characteristics of black carbon concentrations in five marine regions, differing by the outflows of continental aerosol. The largest black carbon content is a salient feature of the atmosphere of the North and Baltic Seas, surrounded by land: average values of concentrations are 210 ng/m3, and modal values are 75 ng/m3. In other regions (except in the south of the Barents Sea), the average black carbon concentrations are 37–44 ng/m3 (modal concentrations are 18–26 ng/m3). We discuss the specific features of the spatial (latitude-longitude) distributions of black carbon concentrations, relying on ship-based measurements and model calculations (MERRA-2 reanalysis data). A common regularity of the experimental and model spatial distributions of black carbon is that the concentrations decrease in the northern direction and with the growing distance from the continent: from several hundred ng/m3 in the southern part of the North Sea to values below 50 ng/m3 in polar regions of the ocean. Full article
(This article belongs to the Special Issue Air Pollution in the Polar Regions: Levels, Sources and Trends)
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Article
Atmospheric Wind Field Modelling with OpenFOAM for Near-Ground Gas Dispersion
Atmosphere 2021, 12(8), 933; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12080933 - 21 Jul 2021
Abstract
CFD simulations of near-ground gas dispersion depend significantly on the accuracy of the wind field. When simulating wind fields with conventional RANS turbulence models, the velocity and turbulence profiles specified as inlet boundary conditions change rapidly in the approach flow region. As a [...] Read more.
CFD simulations of near-ground gas dispersion depend significantly on the accuracy of the wind field. When simulating wind fields with conventional RANS turbulence models, the velocity and turbulence profiles specified as inlet boundary conditions change rapidly in the approach flow region. As a result, when hazardous materials are released, the extent of hazardous areas is calculated based on an approach flow that differs significantly from the boundary conditions defined. To solve this problem, a turbulence model with consistent boundary conditions was developed to ensure a horizontally homogeneous approach flow. Instead of the logarithmic vertical velocity profile, a power law is used to overcome the problem that with the logarithmic profile, negative velocities would be calculated for heights within the roughness length. With this, the problem that the distance of the wall-adjacent cell midpoint has to be higher than the roughness length is solved, so that a high grid resolution can be ensured even in the near-ground region which is required to simulate gas dispersion. The evaluation of the developed CFD model using the German guideline VDI 3783/9 and wind tunnel experiments with realistic obstacle configurations showed a good agreement between the calculated and the measured values and the ability to achieve a horizontally homogenous approach flow. Full article
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Article
An Empirical Atmospheric Density Calibration Model Based on Long Short-Term Memory Neural Network
Atmosphere 2021, 12(7), 925; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070925 - 17 Jul 2021
Abstract
The accuracy of the atmospheric mass density is one of the most important factors affecting the orbital precision of spacecraft at low Earth orbits (LEO). Although there are a number of empirical density models available to use in the orbit determination and prediction [...] Read more.
The accuracy of the atmospheric mass density is one of the most important factors affecting the orbital precision of spacecraft at low Earth orbits (LEO). Although there are a number of empirical density models available to use in the orbit determination and prediction of LEO spacecraft, all of them suffer from errors of various degrees. A practical way to reduce the error of a particular model is to calibrate the model using precise density data or tracking data. In this paper, a long short-term memory (LSTM) neural network is proposed to calibrate the NRLMSISE-00 density model, in which the densities derived from spaceborne accelerometer data are the main input. The resulted LSTM-NRL model, calibrated using the accelerometer data from Challenging Minisatellite Payload (CHAMP) satellite, is extensively experimented to evaluate the calibration performance. With data in one month to train the LSTM-NRL model, the model is shown to effectively reduce the root mean square error of the model densities outside the training window by more than 40% in various time spans and space weather environment. The LSTM-NRL model is also shown to have remarkable transferring performance when it is applied along the GRACE satellite orbits. Full article
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Article
Sensitivity of Simulations of Extreme Mediterranean Storms to the Specification of Sea Surface Temperature: Comparison of Cases of a Tropical-Like Cyclone and Explosive Cyclogenesis
Atmosphere 2021, 12(7), 921; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070921 - 17 Jul 2021
Abstract
Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First [...] Read more.
Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First we assess the impact of specifying SST from two reanalysis data sets with differing spatial resolution. The simulated tropical-like cyclone (TLC) is slightly stronger in the case of the lower resolution SST which is warmer over the formation region, most notably in the maximum rainfall which is ~7% higher. The differences in the two explosive cyclone simulations are negligible, most likely due to intensification occurring mainly over land. We then test the sensitivity of the storms to a range of SST anomalies. The TLC showed a clear trend of increasing storm intensity as SST rises. These results suggest that SST plays a direct role in determining the intensity of the storm. For the explosive cyclone there is no clear trend in dynamical intensity except for the highest warming anomalies. However, the rainfall increases with the magnitude of the SST anomaly. Our results suggest that extreme weather events over the Mediterranean will become more extreme if SST increases as the climate warms, assuming that upper air conditions do not change. Full article
(This article belongs to the Section Meteorology)
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Article
A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months
Atmosphere 2021, 12(7), 914; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070914 - 15 Jul 2021
Abstract
In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., [...] Read more.
In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China. Full article
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Article
Impacts of Non-Local versus Local Moisture Sources on a Heavy (and Deadly) Rain Event in Israel
Atmosphere 2021, 12(7), 855; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070855 - 30 Jun 2021
Abstract
Motivated by poor forecasting of a deadly convective event within the Levant, the factor separation technique was used to investigate the impact of non-local versus local moisture sources on simulated precipitation and lightning rates in central and southern Israel on 25 and 26 [...] Read more.
Motivated by poor forecasting of a deadly convective event within the Levant, the factor separation technique was used to investigate the impact of non-local versus local moisture sources on simulated precipitation and lightning rates in central and southern Israel on 25 and 26 April 2018. Both days saw unusually heavy rains, and it was hypothesized that antecedent precipitation on 25 April contributed to the development of deadly flooding late morning on the 26th, as well as strong lightning and heavy rains later the same day. Antecedent precipitation led to an increase in the precipitable water content and an overall increase in instability as measured by the Convective Available Potential Energy (CAPE). The deadly flood occurred in the area of the Tzafit river gorge (hereafter, Tzafit river), about 25 km southeast of the city of Dimona, a semi-arid region in the northeastern Negev desert. The heavy rains and strong lightning occurred throughout the Levant with local peaks in the vicinity of Jerusalem. Factor separation conducted in model simulations showed that local ground moisture sources had a large impact on the CAPE and subsequent precipitation and lightning rates in the area of Jerusalem, while non-local moisture sources enabled weak convection to occur over broad areas, with particularly strong convection in the area of the Tzafit river. The coupled impact of both moisture sources also led to localized enhanced areas of convective activity. The results suggest that forecast models for the Levant should endeavor to incorporate an accurate depiction of soil moisture to predict convective rain, especially during the typically drier spring-time season. Full article
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Article
Evaluating the Impact of a Wall-Type Green Infrastructure on PM10 and NOx Concentrations in an Urban Street Environment
Atmosphere 2021, 12(7), 839; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070839 - 29 Jun 2021
Cited by 1
Abstract
Nature-based solutions can represent beneficial tools in the field of urban transformation for their contribution to important environmental services such as air quality improvement. To evaluate the impact on urban air pollution of a CityTree (CT), an innovative wall-type green infrastructure in passive [...] Read more.
Nature-based solutions can represent beneficial tools in the field of urban transformation for their contribution to important environmental services such as air quality improvement. To evaluate the impact on urban air pollution of a CityTree (CT), an innovative wall-type green infrastructure in passive (deposition) and active (filtration) modes of operation, a study was conducted in a real urban setting in Modena (Italy) during 2017 and 2018, combining experimental measurements with modelling system evaluations. In this work, relying on the computational resources of CRESCO (Computational Centre for Research on Complex Systems)/ENEAGRID High Performance Computing infrastructure, we used the air pollution microscale model PMSS (Parallel Micro-SWIFT-Micro SPRAY) to simulate air quality during the experimental campaigns. The spatial characteristics of the impact of the CT on local air pollutants concentrations, specifically nitrogen oxides (NOx) and particulate matter (PM10), were assessed. In particular, we used prescribed bulk deposition velocities provided by the experimental campaigns, which tested the CT both in passive (deposition) and in active (filtration) mode of operation. Our results showed that the PM10 and NOx concentration reductions reach from more than 0.1% up to about 0.8% within an area of 10 × 20 m2 around the infrastructure, when the green infrastructure operates in passive mode. In filtration mode the CT exhibited higher performances in the abatement of PM10 concentrations (between 1.5% and 15%), within approximately the same area. We conclude that CTs may find an application in air quality hotspots within specific urban settings (i.e., urban street canyons) where a very localized reduction of pollutants concentration during rush hours might be of interest to limit population exposure. The optimization of the spatial arrangement of CT modules to increment the “clean air zone” is a factor to be investigated in the ongoing development of the CT technology. Full article
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Article
Possible Associations between the Number of Cold Days over East Asia and Arctic Oscillation and Arctic Warming
Atmosphere 2021, 12(7), 842; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos12070842 - 29 Jun 2021
Abstract
Based on the NECP/NCAR reanalysis dataset, the associations between the number of cold days (NCD) over East Asia (100–150° E, 25–55° N) and Arctic Oscillation (AO)/Arctic warming during 1956–2015 are explored. The results show the NCD was closely associated with AO during 1956–1990 [...] Read more.
Based on the NECP/NCAR reanalysis dataset, the associations between the number of cold days (NCD) over East Asia (100–150° E, 25–55° N) and Arctic Oscillation (AO)/Arctic warming during 1956–2015 are explored. The results show the NCD was closely associated with AO during 1956–1990 and Arctic warming during 1991–2015. It reveals NCD over East Asia showed a downward trend and a significantly negative correlation with AO in the previous stage, while it presented an upward trend and notably positive association with Arctic warming in the later period. Meanwhile the increase in the earlier-stage AO will often be accompanied by the weakness of the Siberian high (SH), the Ural Mountains Blocking high (UBH), and the East Asian trough (EAT), and a “positive–negative–positive” wave band exist in the upper troposphere, which is linked with weakened northerly wind over East Asia. All these anomalies are unfavorable for the southward transportation of cold air, eventually leading to the decrease in NCD over East Asia. Additionally, when the near-surface temperature over the Arctic rises in the later period, on the one hand, SH reinforces and further results in more NCD over East Asia; on the other hand, the 1000–500 hPa thickness field displays a “north positive–south negative” pattern, which is conducive to the deceleration of the westerlies at mid-latitudes over Eurasia, and further bring about the enhancement of EAT and UBH, favoring the southward intrusion of cold air, finally, more NCD are generated. Full article
(This article belongs to the Special Issue Asia-Pacific Region: Monsoons and Typhoons)
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