the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Comparing FY-2F/CTA products to ground-based manual total cloud cover observations in Xinjiang under complex underlying surfaces and different Weather Conditions
Shuai Li
Yonghang Chen
Zhili Wang
Xiangyu Li
Yuan Li
Yuanyuan Xue
Abstract. Clouds are an important parameter of artificial water augmentation, which are of substantial significance to judge the precipitation capacity. Xinjiang is an arid region in Northwest China, where weather stations are sparsely distributed, the types of underlying surface are complex and the climate difference between southern and northern Xinjiang varies greatly. However, the retrieval of the total cloud cover (TCC) from satellite in arid areas is a challenging task. Based on the hourly data of TCC observed by ground observation stations from June 2015 to May 2016, considered the complex underlying surfaces and different weather conditions, the precision, consistency and error between the cloud total amount products of FengYun-2F stationary satellite (FY-2F/CTA) and manually observed TCC are compared and evaluated in Xinjiang region. The findings of this study are as follows: (1) The precision rate (PR) of FY-2F/CTA in Xinjiang region is 74.6 %, which gradually decreases from north to south, demonstrating a high false rate (FR) and a low missing rate (MR); The consistency rate (CR) is 51.5 %, with little difference among three sub-regions of Xinjiang, all showing high weak rate (WR) and low strong rate (SR), which means that the TCC inverted from FY-2 satellite data are generally lower than that observed by ground observation stations, especially in Southern Xinjiang; The Bias is -20 %, and all the error indexes (EIs) including Bias, AE and RMSE increase from central to the north and south of Xinjiang, that means the EIs are the lowest in Tianshan Mountains, and the highest in Southern Xinjiang. The PR and CR of FY-2F/CTA in the vegetation underlying surface are better than those of non-vegetation, that is to say, FY-2F/CTA have the best identification effect on the forest and plowland underlying surfaces, and the worst effect on the snow and ice underlying surface. (2) With the increase of temperature, the PR and CR of FY-2F/CTA increase, while the EIs decrease; Under various temperature conditions, FY-2F/CTA have always been exhibiting high MR, low FR (on the contrary in January), high WR and low SR. From low elevation to high elevation, the PR and CR of FY-2F/CTA decrease, but the PR increases significantly when the altitude is higher than 2000 m. (3) Dust reduces the CR of FY-2F/CTA, increases the SR, but it has little effect on the identification of cloud and non-cloud. (4) Under different cloud cover levels, the PR and EIs of FY-2F/CTA are proportional to the amount of TCC, while the CR is inversely proportional to it, that is, the CR is higher, the PR and EIs are lower under clear sky and partly cloudy conditions, and the CR is lower, the PR and EIs are higher under cloudy and overcast conditions. This study is the first to evaluate the FY-2F/CTA on the scales of complex underlying surface, various temperature and altitude, dust effects and different cloud cover levels in arid areas of Xinjiang. Thus, the results would provide an important reference for satellite retrieval and application of TCC in arid areas.
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Shuai Li et al.
Status: final response (author comments only)
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RC1: 'Comment on amt-2023-21', Anonymous Referee #1, 29 Jul 2023
Cloud are the important parameter in weather and climate research . In xinjiang area there are sparsed ground station and the satellite data application is more important .So the validation of satellite data is crucial. The research is meaningful. But there are some comments as following:
1. Line 120 : “2.2 Research data”, the description is too simple. The distribution of the 66 ground based TCC observation should be given, such as see(figure 1). The ground based TCC is about 0 to 10? and the FY-2F/CTA should be 0-100%?
2. Line 133:”where the projection method is Mercator projection, the nearest neighbor method is used for resampling. Secondly, selecting ground-based observations that match the timing of satellite observations”.
(1) Which satellite/CTA data you use? You did Mercator projection? Why use Mercator projection?
(2) “Nearest neighbor method”, what distance?
(3) “match the timing” ,how many minute you use?the same time? Please give the details.3. Line144 to Line 147:”When the observation 145 of ground station is clear sky, but the satellite detection result is cloud, then the effective cloud arithmetic average is performed on the points in a certain area around the point, and if it is still clear sky, then the satellite is judged to have missed the detection, this point is recorded as Yn.” Please check is it right? It’s not consistent with “ ③ When the observation of ground station is clear sky but the satellite detection result is cloud, it would be judged that the satellite misjudgment and be recorded as Ny;”
4. Line 155:“they are considered to be stronger that the values of difference are greater than 2, they are considered to be weaker that the values of difference are less than -2;” and the consistency rate (CR), strong rate (SR) and weak rate (WR) can be expressed as Eq. (5) to Eq. (7) respectively.
is there any cite paper?5. It should give some description for the figures in the paper .For example , with Figure 2, it should tell the reader which is PR distribution, which is the MR distribution at first. The reader will not be confused and search the information in Figures.
The following Figures have the same problems.
6. Line 179: should be 1.375um ,not “gm” .Same Line 1807. Line 186: Line 188: Line 198: FT-2F/CTA is not right.
8. Line 276, “It is observed that with the increase of altitude, the PR and CR of FY-2F/CTA present a decreasing trend”, It seems that decreasing trend is not obvious.
9. All results should be given the numbers of sample. how many matching data author used and got the conclusion? and how about the significance test? Otherwise ,the reader can not be convinced.
10. In “3.3 The difference between FY-2F/CTA products and Manual observed TCC under various cloud cover levels of Xinjiang “. The FY-2F/CLA product’s resolution is 0.1º*0.1º(one point covers 0.1º*0.1º area), ground based TCC data is the station data (scatter data). How to consider and deal with difference of the coverage of two types of data?
11. Line 352: “highe” should be “higher”-
AC1: 'Reply on RC1', Shuai Li, 10 Aug 2023
Dear editor and dear reviewer:
On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript, we appreciate editor and reviewers very much for their positive and constructive comments and suggestions in the interactive discussion of AMT preprint.
We have studied reviewer’s comments carefully and have made revision which marked in red in the paper.We have tried our best to revise our manuscript according to the comments. Please see below our replies in detail. Attached please find the revised version, which we hope reviewer would be satisfied with our answers and the revision we provided.
We would like to express our great appreciation to reviewer for comments on our paper. Looking forward to hearing from you.
Yours sincerely,
Shuai Li
College of Environmental Science and Engineering Donghua University
2999 Renmin North Road, Songjiang District, Shanghai
Mobile: (86)13999856917
Email: rainlishuai@163.com
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RC2: 'Reply on AC1', Anonymous Referee #1, 05 Sep 2023
The author has made modifications and explanations according to the comments provided, and I agree with the author's modifications. But i didn't find the revised paper.
Citation: https://doi.org/10.5194/amt-2023-21-RC2 -
AC2: 'Reply on RC2', Shuai Li, 07 Sep 2023
Dear reviewer:
On the AMT interactive discussion page, attention that “please do NOT submit your revised manuscript here as supplement”, So I could not upload the revised paper. Could you give me a Email, I can send the revised paper to you.
We would like to express our great appreciation to you for comments on our paper. Looking forward to hearing from you.
Yours sincerely,
Shuai Li
College of Environmental Science and Engineering Donghua University
2999 Renmin North Road, Songjiang District, Shanghai
Mobile: (86)13999856917
Email: rainlishuai@163.com
Citation: https://doi.org/10.5194/amt-2023-21-AC2 -
AC3: 'Reply on RC2', Shuai Li, 15 Oct 2023
Dear reviewer:
Since the whole article has been revised in accordance with the second expert's opinion recently, the lines in the article where the specific contents of the revision in the reply to your revision opinion have changed, so we send you a new version of RC1_2.
According to the requirements of the editorial department, the revised full text can be uploaded now, and I have uploaded it.
We would like to express our great appreciation to reviewer for comments on our paper. Looking forward to hearing from you.
Yours sincerely,
Shuai Li
College of Environmental Science and Engineering Donghua University
2999 Renmin North Road, Songjiang District, Shanghai
Mobile: (86)13999856917
Email: rainlishuai@163.com
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AC2: 'Reply on RC2', Shuai Li, 07 Sep 2023
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RC2: 'Reply on AC1', Anonymous Referee #1, 05 Sep 2023
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AC1: 'Reply on RC1', Shuai Li, 10 Aug 2023
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RC3: 'Comment on amt-2023-21', Anonymous Referee #2, 19 Sep 2023
The authors have presented a study of manually derived cloud cover (observational data) and satellite derived data. Comments from the reviewer:
Lines (57-91): A comprehensive comparison between the different studies could benefit this introduction. Is there a patter of what is usually over/underestimated?
Lines 92-106: The region of interest is already being introduced in 2.1. and you are giving here more detail about the data, than in the actual section. At this point it would be better to outline the paper rather than introducing things in detail.
Figure 1: text slipped out of image caption.
Section 2.2: Link should probably be a citation. How is the data collected? What is the satellite instrument? Radiometer?
Abbreviations Ac, TCC and CTA: It is unclear whether Ac is derived for satellite or observations since TCC is used to describe the observations and not satellite. So make sure, that your variables are easy to distinct for someone not familiar with your work.
How many pixels are taken out of Sat data? What's the area you are considering? Does the manual cloud cover extend over the same area?
Figure 2: Fonts too small, cannot see any results.
Figure 3: Green does not translate well visually. Maybe dark green.
Line 175: What is Figure 2 actually showing?
Line 195: Why is the same as NOAA/AVHRR TCCP? Where are the results for NOAA presented?
Figure 5-10: All too small.
Most of the figures are too small and the paper still contains many typos and spelling mistakes (capitol E for Earth for example)
Citation: https://doi.org/10.5194/amt-2023-21-RC3 -
AC2: 'Reply on RC2', Shuai Li, 07 Sep 2023
Dear reviewer:
On the AMT interactive discussion page, attention that “please do NOT submit your revised manuscript here as supplement”, So I could not upload the revised paper. Could you give me a Email, I can send the revised paper to you.
We would like to express our great appreciation to you for comments on our paper. Looking forward to hearing from you.
Yours sincerely,
Shuai Li
College of Environmental Science and Engineering Donghua University
2999 Renmin North Road, Songjiang District, Shanghai
Mobile: (86)13999856917
Email: rainlishuai@163.com
Citation: https://doi.org/10.5194/amt-2023-21-AC2 -
AC4: 'Reply on RC3', Shuai Li, 15 Oct 2023
Dear reviewer:
On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript, we appreciate editor and reviewers very much for their positive and constructive comments and suggestions in the interactive discussion of AMT preprint. We have studied reviewer’s comments carefully and have made revision which marked in red in the paper . We have tried our best to revise our manuscript according to the comments. Please see below our replies in detail. Attached please find the revised version, which we hope reviewer would be satisfied with our answers and the revision we provided. We would like to express our great appreciation to reviewer for comments on our paper. Looking forward to hearing from you.
Yours sincerely,
Shuai Li
College of Environmental Science and Engineering Donghua University
2999 Renmin North Road, Songjiang District, Shanghai
Mobile: (86)13999856917
Email: rainlishuai@163.com
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AC2: 'Reply on RC2', Shuai Li, 07 Sep 2023
Shuai Li et al.
Data sets
FY-2F/CTA products to ground-based manual total cloud cover observations Shuai Li https://doi.org/10.6084/m9.figshare.22015592
Shuai Li et al.
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