Research

34 pages, 14804 KiB

Open AccessArticle

Evaluation of GNSS Radio Occultation Profiles in the Vicinity of Atmospheric Rivers

by Michael J. Murphy, Jr. and Jennifer S. Haase

Atmosphere 2022, 13(9), 1495; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13091495 - 14 Sep 2022

Cited by 2 | Viewed by 1810

Increasing the density of Global Navigation Satellite System radio occultation (RO) with commercial Smallsats and the next generation COSMIC-2 constellation is expected to improve analyses of the state of atmosphere, which is essential for numerical weather prediction. High vertical resolution RO profiles could [...] Read more.

Increasing the density of Global Navigation Satellite System radio occultation (RO) with commercial Smallsats and the next generation COSMIC-2 constellation is expected to improve analyses of the state of atmosphere, which is essential for numerical weather prediction. High vertical resolution RO profiles could be useful to observe atmospheric rivers (ARs) over the ocean, which transport water vapor in shallow, elongated corridors that frequently impact the west coasts of continents. The multi-year AR Reconnaissance campaign has extensively sampled ARs over the northeastern Pacific with dropsondes, providing an invaluable dataset to evaluate the reliability of RO retrievals. These dropsondes, and a reanalysis product that assimilates them, are compared to three RO datasets: (1) established operational missions, (2) COSMIC-2, and (3) the commercial Spire constellation. Each RO dataset has biases relative to reanalyses of less than 0.5% N in the upper troposphere and negative biases in the lower troposphere. Direct colocations with dropsondes indicate that vertical refractivity gradients present within ARs may be contributing to negative biases at higher altitudes inside than outside ARs, where the greatest variability and vertical gradients are at the well-defined boundary layer top. Observations from Spire are overly smooth, affecting the ability to resolve the low-level structure of an AR. Surprisingly, the depth of penetration into the lower troposphere is greater inside an AR than outside for all datasets. The results indicate that the observation errors used for assimilation of RO within ARs should consider the height dependent biases that are associated with the structure of the atmosphere. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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13 pages, 11117 KiB

Open AccessArticle

COSMIC-2 Mission Summary at Three Years in Orbit

by Jan-Peter Weiss, William S. Schreiner, John J. Braun, Wei Xia-Serafino and Cheng-Yung Huang

Atmosphere 2022, 13(9), 1409; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13091409 - 01 Sep 2022

Cited by 13 | Viewed by 2168

Abstract

We summarize the status of the FORMOSAT-7/COSMIC-2 (COSMIC-2) mission which has completed its first three years in orbit. COSMIC-2 is a joint U.S./Taiwan program consisting of six satellites in low-inclination orbits with the following payloads: Global Navigation Satellite System radio occultation, in-situ ion [...] Read more.

We summarize the status of the FORMOSAT-7/COSMIC-2 (COSMIC-2) mission which has completed its first three years in orbit. COSMIC-2 is a joint U.S./Taiwan program consisting of six satellites in low-inclination orbits with the following payloads: Global Navigation Satellite System radio occultation, in-situ ion velocity meter, and tri-band radio frequency beacon. The constellation is in its final orbit configuration and reached mission full operating capability in September 2021. An extensive calibration/validation campaign has to date enabled the release of all baseline neutral atmosphere products and nearly all baseline ionosphere products. The mission is providing usually more than 5000 neutral atmosphere RO profiles per day with a precision better than 2 μrad from 30–60 km altitude. Each day, nearly 12,000 combined total electron content occultations and arcs are generated with absolute accuracy of better than 3 TECU. IVM density precision is at or below the 1% requirement. Neutral atmosphere and ionosphere latency, measured from time of observation to product creation time, is below 30 min median. Data products are delivered in near real-time to operational weather and space weather centers and made available openly to the research community. New ionosphere products specifying the presence and absence of scintillation are under development and planned for future release. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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31 pages, 15894 KiB

Open AccessArticle

GNSS-RO Deep Refraction Signals from Moist Marine Atmospheric Boundary Layer (MABL)

by Dong L. Wu, Jie Gong and Manisha Ganeshan

Atmosphere 2022, 13(6), 953; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13060953 - 11 Jun 2022

Viewed by 1980

Abstract

The marine atmospheric boundary layer (MABL) has a profound impact on sensible heat and moisture exchanges between the surface and the free troposphere. The goal of this study is to develop an alternative technique for retrieving MABL-specific humidity (q) using GNSS-RO [...] Read more.

The marine atmospheric boundary layer (MABL) has a profound impact on sensible heat and moisture exchanges between the surface and the free troposphere. The goal of this study is to develop an alternative technique for retrieving MABL-specific humidity (q) using GNSS-RO data in deep-refracted signals. The GNSS-RO signal amplitude (i.e., signal-to-noise ratio or SNR) at the deep straight-line height (H_SL) was been found to be strongly impacted by water vapor within the MABL. This study presents a statistical analysis to empirically relate the normalized SNR (S_RO) at deep H_SL to the MABL q at 950 hPa (~400 m). When compared to the ERA5 reanalysis data, a good linear q–S_RO relationship is found with the deep H_SL S_RO data, but careful treatments of receiver noise, SNR normalization, and receiver orbital altitude are required. We attribute the good q–S_RO correlation to the strong refraction from a uniform, horizontally stratiform and dynamically quiet MABL water vapor layer. Ducting and diffraction/interference by this layer help to enhance the S_RO amplitude at deep H_SL. Potential MABL water vapor retrieval can be further developed to take advantage of a higher number of S_RO measurements in the MABL compared to the Level-2 products. A better sampled diurnal variation of the MABL q is demonstrated with the S_RO data over the Southeast Pacific (SEP) and the Northeast Pacific (NEP) regions, which appear to be consistent with the low cloud amount variations reported in previous studies. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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24 pages, 18118 KiB

Open AccessEditor’s ChoiceArticle

Advances in Ionospheric Space Weather by Using FORMOSAT-7/COSMIC-2 GNSS Radio Occultations

by Jann-Yenq Liu, Chien-Hung Lin, Panthalingal Krishnanunni Rajesh, Chi-Yen Lin, Fu-Yuan Chang, I-Te Lee, Tzu-Wei Fang, Dominic Fuller-Rowell and Shih-Ping Chen

Atmosphere 2022, 13(6), 858; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13060858 - 24 May 2022

Cited by 12 | Viewed by 2337

Abstract

This paper provides an overview of the contributions of the space-based global navigation satellite system (GNSS) radio occultation (RO) measurements from the FORMOSAT-7/COSMIC2 (F7/C2) mission in advancing our understanding of ionospheric plasma physics in the purview of space weather. The global positioning system [...] Read more.

This paper provides an overview of the contributions of the space-based global navigation satellite system (GNSS) radio occultation (RO) measurements from the FORMOSAT-7/COSMIC2 (F7/C2) mission in advancing our understanding of ionospheric plasma physics in the purview of space weather. The global positioning system (GPS) occultation experiment (GOX) onboard FORMOSAT-3/COSMIC (F3/C), with more than four and half million ionospheric RO soundings during April 2006–May 2020, offered a unique three-dimensional (3D) perspective to examine the global electron density distribution and unravel the underlying physical processes. The current F7/C2 carries TGRS (Tri-GNSS radio occultation system) has tracked more than 4000 RO profiles within ±35° latitudes per day since 25 June 2019. Taking advantage of the larger number of low-latitude soundings, the F7/C2 TGRS observations were used here to examine the 3D electron density structures and electrodynamics of the equatorial ionization anomaly, plasma depletion bays, and four-peaked patterns, as well as the S4 index of GNSS signal scintillations in the equatorial and low-latitude ionosphere, which have been previously investigated by using F3/C measurements. The results demonstrated that the denser low-latitude soundings enable the construction of monthly global electron density maps as well the altitude-latitude profiles with higher spatial and temporal resolution windows, and revealed longitudinal and seasonal characteristics in greater detail. The enhanced F7/C2 RO observations were further applied by the Central Weather Bureau/Space Weather Operation Office (CWB/SWOO) in Taiwan and the National Oceanic and Atmospheric Administration/Space Weather Prediction Center (NOAA/SWPC) in the United States to specify the ionospheric conditions for issuing alerts and warnings for positioning, navigation, and communication customers. A brief description of the two models is also provided. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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20 pages, 4784 KiB

Open AccessArticle

Comparison of COSMIC and COSMIC-2 Radio Occultation Refractivity and Bending Angle Uncertainties in August 2006 and 2021

by Richard Anthes, Jeremiah Sjoberg, Xuelei Feng and Stig Syndergaard

Atmosphere 2022, 13(5), 790; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13050790 - 12 May 2022

Cited by 11 | Viewed by 2128

Abstract

We compare the random error statistics (uncertainties) of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate, C1) and COSMIC-2 (C2) radio occultation (RO) bending angles and refractivities for the months of August 2006 and 2021 over the tropics and subtropics using the [...] Read more.

We compare the random error statistics (uncertainties) of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate, C1) and COSMIC-2 (C2) radio occultation (RO) bending angles and refractivities for the months of August 2006 and 2021 over the tropics and subtropics using the three-cornered hat method. The uncertainty profiles are similar for the two RO missions in the troposphere. However, a higher percentage of C2 profiles reach close to the surface in the moisture-rich tropics, an advantage of the higher signal-to-noise ratio (SNR) in C2. C2 uses signals from both GPS (Global Positioning System) and GLONASS Global Navigation System Satellites (GNSS). The GPS occultations show smaller uncertainties in the stratosphere and lower mesosphere (30–60 km) than the GLONASS occultations, a result of more accurate GPS clocks. Therefore, C2 (GPS) uncertainties are smaller than C1 uncertainties between 30–60 km while the C2 (GLONASS) uncertainties are larger than those of C1. The uncertainty profiles vary with latitude at all levels. We find that horizontal gradients in temperature and water vapor, and therefore refractivity, are the major cause of uncertainties in the tropopause region and troposphere through the violation of the assumption of spherical symmetry in the retrieval of bending angles and refractivity. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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14 pages, 2271 KiB

Open AccessEditor’s ChoiceArticle

Ionospheric Variability during the 2020–2021 SSW: COSMIC-2 Observations and WACCM-X Simulations

by Nicholas Pedatella

Atmosphere 2022, 13(3), 368; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13030368 - 22 Feb 2022

Cited by 6 | Viewed by 2125

Abstract

Variability in the ionosphere during the 2020–2021 sudden stratospheric warming (SSW) is investigated using a combination of Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) observations and the Whole Atmosphere Community Climate Model with thermosphere–ionosphere eXtension (WACCM-X) simulations. The unprecedented spatial–temporal sampling [...] Read more.

Variability in the ionosphere during the 2020–2021 sudden stratospheric warming (SSW) is investigated using a combination of Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) observations and the Whole Atmosphere Community Climate Model with thermosphere–ionosphere eXtension (WACCM-X) simulations. The unprecedented spatial–temporal sampling of the low latitude ionosphere afforded by COSMIC-2 enables investigating the short-term (<5 days) variability in the ionosphere during the SSW event. The COSMIC-2 observations reveal a reduction in the diurnal and zonal mean ionosphere total electron content (ITEC) and reduced amplitude of the diurnal variation in the ionosphere during the SSW. Enhanced ITEC amplitudes of the semidiurnal solar and lunar migrating tides and the westward propagating semidiurnal tide with zonal wavenumber 3 are also observed. The WACCM-X simulations demonstrate that these variations are driven by variability in the stratosphere–mesosphere during the 2020–2021 SSW event. The results show the impact of the 2020–2021 SSW on the mean state, diurnal, and semidiurnal variations in the ionosphere, as well as the capabilities of the COSMIC-2 mission to observe short-term variability in the ionosphere that is driven by meteorological variability in the lower atmosphere. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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26 pages, 2833 KiB

Open AccessArticle

Distinguishing Convective-Transition Moisture-Temperature Relationships with a Constellation of Polarimetric Radio Occultation Observations in and near Convection

by F. Joseph Turk, Ramon Padullés, David D. Morabito, Todd Emmenegger and J. David Neelin

Atmosphere 2022, 13(2), 259; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13020259 - 02 Feb 2022

Viewed by 1904

Abstract

Convective transition statistics serve as diagnostics for the parameterization of convection in climate and weather forecast models by characterizing the dependence of convection on the humidity-temperature environment. The observed strong pickup of precipitation as a function of layer-averaged water vapor and temperature is [...] Read more.

Convective transition statistics serve as diagnostics for the parameterization of convection in climate and weather forecast models by characterizing the dependence of convection on the humidity-temperature environment. The observed strong pickup of precipitation as a function of layer-averaged water vapor and temperature is captured in models with varying accuracy. For independent observational verification, a low-Earth orbiting satellite constellation of Global Navigation Satellite System (GNSS) polarimetric radio occultation (PRO) measurements would be spaced such that adjacent RO would capture different profiles within and immediately adjacent to convection. Here, the number of profile observations needed to distinguish between convective transition relations by different tropospheric temperature ranges is determined, over different tropical oceanic basins. To obtain these, orbit simulations were performed by flying different satellite constellations over global precipitation from the Global Precipitation Measurement (GPM) mission, varying the numbers of satellites, orbit altitude, and inclination. A 45-degree orbit inclination was found to be a good tradeoff between maximizing the number of observations collected per day, and the desired 50–150-km spacing between individual RO ray paths. Assuming a set of reasonable assumptions for net data yield, three tropospheric temperatures can be distinguished by 1 K with a six-month on-orbit duration from a constellation of at least three satellites. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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25 pages, 12326 KiB

Open AccessArticle

Relationships between Extratropical Precipitation Systems and UTLS Temperatures and Tropopause Height from GPM and GPS-RO

by Benjamin R. Johnston, Feiqin Xie and Chuntao Liu

Atmosphere 2022, 13(2), 196; https://0-doi-org.brum.beds.ac.uk/10.3390/atmos13020196 - 26 Jan 2022

Viewed by 1988

Abstract

This study characterizes the relationship between extratropical precipitation systems to changes in upper troposphere and lower stratosphere (UTLS) temperature and tropopause height within different environments. Precipitation features (PFs) observed by the Global Precipitation Measurement (GPM) satellite are collocated with GPS radio occultation (RO) [...] Read more.

This study characterizes the relationship between extratropical precipitation systems to changes in upper troposphere and lower stratosphere (UTLS) temperature and tropopause height within different environments. Precipitation features (PFs) observed by the Global Precipitation Measurement (GPM) satellite are collocated with GPS radio occultation (RO) temperature profiles from 2014 to 2017 and classified as non-deep stratospheric intrusion (non-DSI; related to convective instability) or deep stratospheric intrusion (DSI; related to strong dynamic effects on the tropopause). Non-DSI PFs introduce warming (up to 1 K) in the upper troposphere, transitioning to strong cooling (up to −3.5 K) around the lapse rate tropopause (LRT), and back to warming (up to 2.5 K, particularly over the ocean) in the lower stratosphere. UTLS temperature anomalies for DSI events are driven predominantly by large scale dynamics, with major cooling (up to −6 K) observed from the mid-troposphere to the LRT, which transitions to strong warming (up to 4 K) in the lower stratosphere. Small and deep non-DSI PFs typically result in a lower LRT (up to 0.4 km), whereas large but weaker PFs lead to a higher LRT with similar magnitudes. DSI events are associated with larger LRT height decreases, with anomalies of almost −2 km near the deepest PFs. These results suggest intricate relationships between precipitation systems and the UTLS temperature structure. Importantly, non-DSI PF temperature anomalies show patterns similar to tropical convection, which provides unification of previous tropical research with extratropical barotropic convective impacts to UTLS temperatures. Full article

(This article belongs to the Special Issue Advances in GNSS Radio Occultation Technique and Applications)

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