The Impact of Rainfall on Soil Moisture Variability in Four Homogeneous Rainfall Zones of India during Strong, Weak, and Normal Indian Summer Monsoons
Round 1
Reviewer 1 Report
The paper "The impact of rainfall on soil moisture variability in four homogeneous rainfall zones of India during strong, weak and normal Indian summer monsoons" explores the question of how the soil moisture is governed by rainfall in four regions in India during the Indian Summer Monsoon (ISM). The study was performed with long data sets of daily data which means that the results can be expected to be robust. I was happy to see the authors state an important caveat which is that the rainfall data and soil moisture data, though both are daily, they are accumulated from different starting points which give a 3 hour shift in timing.
This study is not hugely novel, but it does do a good job of exploring longer data sets at daily resolution to help answer important questions about the relationship of rainfall to soil moisture. These relationships are critical to understand in the context of the monsoon and in India, a country where agriculture is very important and so many people are affected by meteorological influences on local food production. I think that there are several issues which once addressed could help with the clarity of the paper and the accessibility to readers.
Main questions for the authors.
1. In the abstract the sentence in lines 20-22 does not make sense to me. There are 2 parenthetical comments "during June(June-July) of strong (weak) ISMs where SM values are relatively small". If one removes the words in parentheses it makes sense. Could clearer be to do that, then write a second sentence which explains the other point you and co-authors are trying to make.
2. In one case the authors discuss a statistical significance greater than 95% and say that this is a test of whether the correlation is significantly different from zero. In other places, when they discuss significance, they don't mention whether they have the same null hypothesis for each time they apply the test. Could the significance testing be clarified for each case with a sentence or two perhaps?
3. Around line 225, "Monthly rainfall differences ... are not statistically significant..." was a bit surprising. Perhaps point the reader back to Figures 3 row 3 when you state this.
4. Section 3.2.2 In table 2 where the authors highly "significant values" I wonder if choosing difference from zero as the test is not obscuring a result? It appears that we have significant (if low) values for each of the regions in at least one month for all three regimes (Strong, weak and normal). Would it make more sense to assess significance against a higher correlation value?
5. I do not think that the statement L 317 "During the mature and withdrawal phases, the rain explained variance during weak ISM is overall larger than for strong ISM... " is supported by the numbers in table 2. For example, the difference in correlation between strong and weak for Sept. in CI is 0.55 and 0.52. These are similar correlations. Please can you examine this paragraph and check whether you can really draw all the conclusions you have drawn from the numbers given?
Minor revisions.
1. All figures except for figure 2 are using color choices that do not lend themselves to interpretation by colour blind readers. The choice of red and green and the choice of jet/rainbow should be replaced in all of the figures. I leave it to the authors to change as they see fit, but if I may suggest some helpful tips:
1a. replace red/green lines with red/blue or purple/green and even better, don't let colour be the only marker of difference. Please change one of the solid lines to dash or dash-dot.
1b. replace the rainbow palette with a ColorBrewer palette https://colorbrewer2.org/#type=qualitative&scheme=Accent&n=3
1c. In figure 1 can the red (NWI) or green (CI) be switched to another colour to avoid this issue?
Two helpful links are:
https://davidmathlogic.com/colorblind/#%23D81B60-%231E88E5-%23FFC107-%23004D40
https://www.visualisingdata.com/2019/08/five-ways-to-design-for-red-green-colour-blindness/#:~:text=The%20pink%2Dred%20through%20to,green%20hues%20used%20by%20default.
2. Please can the units be displayed next to the colour bars? And please can rows or columns be labeled in the multi-plots (e.g. Figures 3 and 4) to help when referring back from the text?
3. Figure captions, suggested changes:
3a. Fig 3 caption has soil moisture and its units in the caption, but soil moisture is not plotted here. Remove that and place in figure caption 4.
3b. Figure 7 has incorrect year range: "1992-20120" please amend.
3c. Figure 9 could state more clearly what the slope is. How is it computed?
4. What do the white stippled lines in Figures 3 and 4 represent? They occur south of 25 degrees N in each plot. I can't find the explanation for why this is there.
5. Please can a reference be given in the Introduction for the 4 Indian regions and how they are determined? "... the IMD defined four so-called regions..." but there is no citation of the IMD publication or website here. I note that there is a paper by Ramu et.al. in the Journal of Hydrology (Volume 546, March 2017) that divides India into more than 4 regions: https://www.sciencedirect.com/science/article/pii/S0022169417300124
6. Several sections consist of very long paragraphs that should be split into smaller paragraphs. Please change sections 3.2.3 "Spatial variations..." and 6 "Discussion". If you can review the other longer paragraphs throughout the paper, you might be able to rewrite them into easier to follow short paragraphs.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Line 40: “… and other terms are sinks …”. Which are the other terms?
Lines 107-109: How is the impact of rainfall isolated?
Line 179: “To further reduce the possible effect of runoff …”. Which variable in Eq. (1) is the runoff? Is this the variable TR? However, TR in Eq. (1) is characterized as horizontal and downward transport.
Line 179-182: How is the correlation mentioned here used in order to reduce the possible effect of runoff?
Section 3.2.1, lines 254-263: It is not clear why it is acceptable to assume that SM depends only on rainfall alone. How strong could be the modification of the results presented here if the effect of ET and TR (see equation (1)) could be considered?
The same question arises also for the results in sections 3.2.2 and 3.2.3.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
In general, the manuscript shows exquisite care in the presentation of the work undertaken
· The abstract summarises well the scope and overall results of the work
· The introduction states well the conditions under which the study has been developed with respect to the application area, in situ and satellite measurements. It also gives an account of previous similar studies, showing the originality and complementarity of their work with respect to those
· The data used are also well explained, their sources and specifications, etc. This is also applicable to the classification and significance of the ISMs over the IMD regions
· The methods applied, although not really complex, however they were designed to cover the significant statistical parameters and explain eventual deviations and anomalies in the results. As a consequence,
· The results and their interpretations are excellently shown, covering
o the spatial and temporal distributions of SM and rainfall
o the SM dependence on rainfall according to the different ISMs
o Explanation of the daily SM variance (and spatial variation) through daily rainfall
· The discussion is very well stated as well as the conclusions of their study
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
