Cloud Overlap Features from Multi-Year Cloud Radar Observations at the SACOL Site and Comparison with Satellites

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review report of

Cloud overlap features from multi-year cloud radar observations at SACOL site and comparison with satellites

By Yang et al.

Summary of paper:

This paper presents the cloud overlap properties with a ground-based Ka-band cloud radar at the SACOL site, which is located in the arid and semi-arid regions. The authors gave a nice review of the algorithms to calculate the cloud overlap parameters commonly used in the community with different hypotheses. Based on the statistical analysis of multi-year radar observations from 2013-2019, the authors determined the statistical properties of cloud overlap parameters, decorrelation lengths and cloud fraction as well as their seasonal variations with the assumptions of different temporal and vertical spatial resolutions as well as for different cloud types. They further compared the results from the ground-based radar observations with the satellite observations covering different areas and reached an overall good agreement between them, except for CALIPSO.

 

General comments:

The research topic of cloud overlap detections and their parameterization in the atmosphere models is very interesting and important and certainly relevant to the readers of remote sensing. The authors have a unique dataset with remote sensing instruments at their disposal that are certainly valuable for the corresponding research. The manuscript is well written and organized and of course deserves to be published. However, there are several points should be clarified before publication.

Different probing techniques have different spatial coverage: the space-borne lidar (CALIOP) and radar (CPR) certainly have a different volume and CPR and KAZR operating at different frequencies (94 vs 35 GHz) may also possess different probing volume. It means that some clouds may be only seen by one instrument but invisible to others. Therefore, the necessary discussions or significance test should be given when the comparisons between them are conducted. Of course, the statistical analysis based on abundant datasets makes the comparison convictive. Nevertheless, discussions on this issue are still needed.

The method used in the manuscript is not new, but has intensively been applied in the previous studies. So, the Section of methodology could be made shorter.

The conclusion (Section 5) is missing and, of course, should be added.

Typos and suggestions listed as follows (but not limited to):

1.       Line 36, suspended -> suspending;

2.       Line 46, what do you mean by “in natural settings”? Please indicate in more details.

3.       Line 47, to remove “but”;

4.       Lines 71-75, Please add relevant references;

5.       Line 85, two monthly observation -> two-month observations;

6.       Line 101, any references to back up “These studies ...”? Please add;

7.       Line 142, Section 5 is missing; (!)

8.       Line 158, Space-born -> Space-borne;

9.       Line 173, comprises -> comprises of;

10.   Lines 183-184, Do you compare MODIS to CALIPSO with the statement “a higher horizontal spatial resolution”? Do you have any references to back this statement up? I don’t think this is the case. Please check and correct it.

11.   Lines 192-193, Please rephrase the sentence;

12.   Line 206, in Panel b (left part), it looks like Ctrue = 0.9 and TCF= 1.0. Please also add the blue lines and red markers to give a clearer view of modularization;

13.   Line 2016, to remove “are”;

14.   Lines 223 and 233, the commas in equation (2) and (3) are very misleading and should be reformulated;

15.   Lines 228-230, Please add relevant references;

16.   Lines 231-232, Please indicate what Lcf and deltaZ are, although they are already mentioned in Introduction;

17.   Line 234-235, what do you want to express with this sentence “thus, …”?

18.   Line 257, the six cloud types should be mentioned and defined in details earlier for the sake of easy-reading;

19.    Line 266, do you use ERA-interim or ERA-5. To be precise;

20.   Lines 275-276, please complete the sentence;

21.   Line 298, seasons -> seasonal;

22.   Lines 301-302, which part or figure back this statement up?

23.   Line 305, it would be better to be updated with a higher-quality figure;

24.   Line 305, during -> within;

25.   Lines 419-420, what are the reasons contributing to the large departure of CALIPSO results from others? More explanations will help;

26.   Line 434, Please adjust the y-axis range of panel d to the ones used in other panels for a better view of comparison;

27.   Line 499, it’ll be friendly for reader to update Figure 10 with better qualities;

28.   Line 501, why don’t you just use median and interquartile or mean and standard deviation?

29.   Lines 509-510, impact factors -> potential impacts;

30.   Lines 523-525, please rephrase the sentence;

31.   Line 526, significant season change trend -> a significant trend in the seasonal variations;

32.   Lines 531-532, the remaining four CFs -> the CFs of the four remaining cloud types;

 

 

Comments on the Quality of English Language

The manuscript is well written and easy to understand. However, it is absolutely necessary to go through the context and make some corrections to typos and grammatical mistakes. Some of them have been pointed out in the general comments above.  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper of Xuan Yang  et al., presents the Cloud overlap features from multi-year cloud radar observations at SACOL site and comparison with satellites. The results are interesting, however more work must be done, regarding the definitions used. Minor revisions are needed, and all the following comments must be addressed before accepting the manuscript for publication.

General comment

Line 18-19. The authors claim that: «Our findings show that cloud overlap parameters and total cloud fraction are maximized during winter-spring and minimized in summer-autumn». In which Figure they base their assumption?

 

Line 19. The authors claim that: «…with decorrelation length variations lagging by quarters». What do they mean? Which is the definition of the “decorrelation length” ?

Line 142. «Section 5 summarizes the conclusion. »Please correct this, there is no Section 5.

Session 2.2.1 «Active satellite sensors» and Session 2.2.2 «Passive satellite sensor» lack of references. The authors must provide the appropriate literature on the Space-born active and passive observations.

Line 249. «…resolution.Increasing…». The two sentences must be corrected.

Line 267. «…altitudes.. ». The sentence must be corrected.

How “cloud fraction” is defined?

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present a study on cloud overlap and cloud classification based on cloud height. Both are important parameters in various atmospheric models. For their study, they used extensive datasets of ground-based radar and satellite-borne remote sensing instruments. The main finding is, besides the description of these cloud parameters above a specific site, the technique to estimate optimal temporal and spatial resolutions in the retrieval those parameters.

The paper fits into the scope of Remote Sensing, and it is exceptionally well written, eventhouth a bit lengthy. Therefore, I recommend publication after some minor clarifications and text edits. Please, see the attached pdf.

 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf