Changes in the Frequency of Extreme Cooling Events in Winter over China and Their Relationship with Arctic Oscillation
Round 1
Reviewer 1 Report
This manuscript by Song and Yan carried out a detailed analysis on the features of extreme cold events in China, during the 1967-2017 period, from the perspective of the relationship with high-latitude circulation patterns, i.e., the Artic Oscillation. These findings attach important information about changes in cold events in China that could deepen our understanding on cold-related extreme events. The manuscript may be interesting for different stakeholders since this type of events has a highly disruptive potential causing great economic losses and adverse social impacts. The manuscript is clearly written and well structured.
However, I have serious concerns related with extreme event definition and the threshold calculation that needs clarification.
As I understand it TCN < 0 per se represents the drop on mean temperature between day and the previous day. The result is a series of n-1 consecutive or single day negative and positive values. Next the TCN series is sorted from lowest to highest and p90th is found. Correct me if I’m wrong but doesn't this identify the highest positive value? See my interpretation below.
| day | previous day | TCN | sort TCN | only TCN negative | |
| -7 | -4 | -3 | -3 | -3 | |
| -9 | -7 | -2 | -2 | -2 | |
| -11 | -9 | -2 | -2 | -2 | |
| -12 | -11 | -1 | -1 | -1 | |
| -13 | -12 | -1 | -1 | -1 | |
| -12 | -12 | 0 | 0 | ||
| -12 | -12 | 0 | 0 | ||
| -11 | -12 | 1 | 1 | ||
| -10 | -11 | 1 | 1 | ||
| -8 | -10 | 2 | 2 | ||
| -6 | -8 | 2 | 2 | ||
| -3 | -6 | 3 | 3 | ||
| p90 | 2 | -1 | |||
| p10 | -2 | -2.6 |
If my understanding is correct it seriously compromises the results, and I accepted the manuscript after a major revision. If I am wrong about this appreciation, please accept my apologies and I recommended it to be accepted after a minor revisions.
In the manuscript it is necessary:
General comments
First, clarify the identification of the extreme event and the threshold calculation.
I understand that the SI unit for year is a (annum) but it is common practice use “y” or “yr”. My concern is related to the fact that this may cause some confusion to the reader.
Another concern is when presenting the results in abstract section. I would suggest round numbers to the nearest single-digit whole number or to a reasonable number of significative algorisms to make the structure much clearer. E.g., it is easier to read “0.7 days in the last 57 years” than 0.730 days in the last 57 years” (L 13).
Why use of mean temperature instead of the minimum temperature? I would suggest adding a briefly explanation.
If I understood correctly, in line 69-70 the authors mention that recent studies show a positive correlation between AO and winter temperatures. However, in this study the correlation is negative. It sounds like a contradiction. Please, clarify this.
Minor comments:
L 13 - 57 a -> 57 yr
L 14 - -0.128 d/10 a -> 0.1 d/10 a or 0.1 d/10 yr
L 15 4.373 d -> 4 d or 4 days
L 16 –0.459->0.5
21.1% -> 21%
L 52 –“However, most definitions are based on absolute thresholds” Some references should be added.
L 56 – REOF? Full name, please.
L 66 – AO?? First time mention in the text needs full name. “.. Artic Oscillation (AO) …”
Figure 3/4/7 – Missing colorbar label.
Figure 5 – Missing y-axis label.
Figure 6 – Quantify the colors and explain the meaning of the p<0.05.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The authors of the manuscript entitled " Changes in the frequency of extreme cooling events in winter over China and their relationship with artic oscillation" tried to present the spatial and temporal frequencies of EC events over China. The manuscript looks promising however lacks scientific originality. Also the authors have failed to explore the potential implications of the reduced/increased EC events which they mentioned as a challenge to socio-economy and human health in the abstract section. To improve the quality of the manuscript, I suggest to incorporate following comments:
- The originality of the manuscript is not clearly understood. Why this research is required?
- The application of the current research to end user would be an advantage
- In case of the spatial distribution, rather than geographical distribution only, climatological distribution ( arid and cold regions) would be better
- A clear connection of using observed and reanalysis data is not clearly understood. why the authors used reanalysis data when they have temperature data available from China Meteorological Administration?
- The English and grammar of the manuscript need to be improved.
- Please check the regression equation in Figure 2. In the same figure is the solid black line for whole China? It would be better if you plot for different regions as shown in Figure 1 which would help to compare where the events are changing.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I would like to thank the authors for addressing my initial comments. The authors have responded to all my questions and made the necessary changes to the manuscript which has much improved this manuscript. The latest version of the manuscript includes changes and results that are well presented with much interpretation which mostly fulfil my previous concerns. I appreciate the efforts of the authors in producing this recent version. I think that now it is better written, the new abstract establishes more clearly the objectives and methods of the paper, the figures are well. All the major points had been addressed.
Overall, I would recommend this manuscript for publication.
Reviewer 2 Report
Thank you for responding the comments I made.
