Comment on hess-2021-524

moisture contributed from the IP (26%), the west region (57%), and the east region (17%), and (3) the reduction in local recycling closely links to a decrease in summer precipitation. These results can help us to better understand changes in precipitation over the study region.

The results help us to understand the hydrological system of the IP better as the authors analyzed spatial and temporal characteristics of water resources of their study region. By splitting the precipitationshed up in different source areas we can get a better understanding of the role of different physical processes in the cycling of continental water.
I believe this is an interesting and relevant article, that fits to the scope of this journal. However, revisions are necessary before I recommend this article for publication.

Strengths
I believe the goal, methods, and results of this study are clearly described and presented. I find this a very interesting study. The figures are very informative and clear. I only have some minor comments about the figures and captions (See minor comments). Furthermore, I like the table in the discussion as it gives a nice clear overview of the change in contribution of the three source regions.

Main points of improvement
First, this study uses data with a spatial scale of 1x1 degree. I was wondering why the authors decided to use data with a resolution of 1 degree in this study. WAM-2layers is mostly run at a spatial scale of 1.5 degree (e.g. Link et al., 2020). Tuinenburg and Staal (2020) showed that the time step and grid cell size can influence the output of the simulation when using a Eulerian model. If the grid cells become too small, which normally could happen at high latitudes, the Courant number could become larger than 1. If the Courant number is larger than 1, moisture cannot be correctly transported over a Eulerian grid (Tuinenburg and Staal, 2020). The authors decided to use a smaller spatial resolution than 1.5 degree, which will affect the Courant number. Therefore, I would be interested in a clarification of the authors on if the change in spatial resolution affects the output of their model.
Second, I believe that the physical processes that drive the transport of moisture to the IP should be highlighted a bit better. It would be very interesting if it is possible to support the decrease in the contribution of the different regions with a change in these physical processes, or the importance of these physical processes. This is done for the contribution of the western region. The authors describe how an increase in surface temperature over land reduces rainfall. I am interested in such an explanation for the other two source regions as well. In the discussion, the authors use the change in summer evaporation to elaborate a bit on this point as well. However, while reading this part, I was wondering how the summer evaporation relates specifically to the dry years. Perhaps the authors could elaborate on this. In addition, Table 1 shows the important contribution of a change in the western source for summer as well. Perhaps the authors could clarify, using the physical mechanisms, why the focus in this article is on the local moisture recycling and not on the western source region.
Third, I think the authors should highlight the relevance of the research a bit better. I believe this manuscript would be more informative if the authors clearly describe the implication of their results. The scientific relevance is described as follows: a better understanding of the summer precipitation decline in the IP. However, I miss what this additional understanding could be used for. Please, describe this relevance in the discussion and shortly mention it in the conclusion.
Finally, I was wondering why the authors call the recycling of moisture within the IP local recycling and not regional recycling as the moisture recycles within a region. The reader could misunderstand the spatial scale of this study when reading local moisture recycling as local scale could be understood as a smaller spatial scale than the spatial scale of the IP. This misunderstanding can be prevented when the authors state their definition of local recycling in the introduction, or when they use the terminology regional recycling. The latter would prevent misunderstanding the title.

Minor points concerning figures and tables
In multiple captions the letter indicating which plot a specific part in the caption is about, is sometimes located in front of the subject and sometimes behind the subject. Please, change this so all captions are consistent. I.e. either the letter in front or behind the part of the caption it refers to.
For figure 2, the y-axis for some of the plots starts at zero and for some of the plots it does not. However, I believe it would be easier to compare the result if the y-axis of all plots start with zero. Could the authors please consider this?
For figure 3, 4, 7 and 8, the colorbar indicates the unit of the quantity the authors plot here. Please also indicate what quantity is plotted above the colorbar. This will make the plots easier to read.
For figure 5, could the authors please make a small change in the caption? Please clarify it is the precipitationshed of the IP.
For figure 6, it took me some time to understand plot (b) has two y-axes. This could be clarified by changing the color of the left y-axis to blue.
In the caption of Figure 7, the authors indicate how they calculated the difference between wet and dry years. However, for Figure 8 the authors did not include such a description. Please add this to the caption of Figure 8.

General minor points
In the abstract (line 19) the authors mention the source. By using 'the source' it seems like there is only one source. Please rephrase to sources or mention the three main sources that are studied in this research.
In the introduction (line 33), the authors state the IP is located in the Mediterranean area. However, there are five major Mediterranean areas around the world. Please rephrase to the Mediterranean basin which is one of these five Mediterranean areas.
In the description of the study areas the authors describe the topography with the word high (line 93). Do the authors refer to elevation here? If so, please clarify by using a word like elevated.
In Equation (1) the authors use a +/-sign in front of the vertical moisture transport term. I can imagine this is because of the direction of the transport. However, if it is negative isn't the minus already implemented in the F term? In addition, when reading this article I was wondering what the residual term presents. Please clarify both points.
In Equations (2) and (3) the authors use the sign for a cross product. However, do the authors want to indicate a cross product or a product?
The sentence of lines 150-152 is a bit unclear to me. Could the authors rephrase this sentence?
The mutation test and the term mutation are new to me. Reading the article I understand this test can be used to find a significant change within data. Please include an explanation on this in one sentence (or a few) around line 159.
Line 191, the authors mention both Iberia01 and ERA5 show statistically significant changes in 1997. I would like to ask the authors to indicate this with a number resulting from their mutation analysis.
In line 211, the authors use the words 'are separated'. This use of words is a bit unclear to me. Do the authors mean that the dry years stand out?
In lines 215-217, the sentence is a bit unclear to me. I believe the authors state that the average precipitation between 1980 and 2019 is 28.53 mm per month and that for these years the summer precipitation in the IP is on average 30.64 mm per month. This indicates that the summer precipitation is above average. However, Mediterranean areas are wet in winter and dry in summer. Therefore, this result seems to be unexpected. Please elaborate on this.
In line 254, could the authors indicate the percentage of the reduction of 3 mm per month?
In lines 323-324, the authors state that the disappearance of wet years in the second time period motivates changes similar to a higher contribution of all three areas to precipitation in the IP. This statement is a bit vague to me. Perhaps because the authors use the word motivate. Do the authors mean to say that they see a similar pattern? If so, could the authors please rewrite this sentence?
In the first lines of the conclusion, the authors state 'moisture contribution from the source'. However, in their study the authors focused on three source regions. I believe the conclusion would improve if the authors mention the three sources here. This nicely links to point 2 in the conclusion where the authors mention the regions. If these regions are already introduces in the beginning of the conclusion, this part might become easier to read.

Minor points in use of grammar
The sentence in lines 71-74 is a bit unclear to me due to the sub sentence in the middle. I had to read it multiple times to understand it properly. Please rephrase.