Review of "Compound droughts under climate change in Switzerland" von Matt et al.

The topic of compound droughts is pressing and important, and the authors have contributed very nicely in identifying them and using scenarios to see how they might change in a warming climate, using transient climate and hydrological scenarios for Switzerland.

The paper is clearly structured and well written and provides a comprehensive and convincing introduction to the topic. 

For some of the underlying assumptions and control model performance tests, the authors refer to previous studies (catchments and calibration validation performance). I think it is important to provide this information directly in the paper or in its appendix to understand the basis on which the scenarios were used and how reliable the models were. Looking at the referenced paper, it appears that the NSE was used to calibrate the models and the KGE and NSE were used to validate them. I would expect that particularly low flow periods would not be so well simulated, or at least not evaluated in the objective function. Perhaps this could also be mentioned in the discussion of uncertainty in the discussion.

As a minimum I would expect a table with the main characteristics of the catchments used, rather than just a map, including mean annual precipitation, mean annual discharge, altitude (range), glaciation percentage, size and some model performance in calibration and validation. The authors state at the end of their discussion that it is important to better understand the processes that lead to these compound droughts, and I believe that to understand these we also need to look at these catchment characteristics and therefore provide them in some form as well.

Other than that, I really enjoyed reading the paper and have very few and small technical comments:

L135 please add what the Hamon equations use as main variables to calculate PET (lon, lat, air temperature)

L139 what does "satisfactorily" mean in terms of performance, please specify 

L441 Section ???

Revision of the manuscript number “nhess-2024-6” entitled “Compound droughts under climate change in Switzerland”.

This manuscript contributes to analyzing compound droughts in different catchments in Switzerland under two circumstances: modelling present and forecasting future climates. The paper is well-structured and written overall and can be published in its present form. I have a few technical comments:

1. L28. Change redaction.

2. L54. What do you mean by “strongly non-linear”? Be more specific with the degree or type of the function, or just mention it as “non-linear”.

3. L55. Avoid using qualifiers such as “strongly”, instead, be more specific with the type of relationship between the variables.

4. L103-L106. Improve redaction.

5. L119-L120. It could be better if you slightly describe what you show in every single section, not only writing the section title.

6. L123. Fix units. 1702 km² and 1500 m.a.s.l.

7. Figure 7, the label on the ordinate might be better if it says "probability".