Overall, this manuscript makes a nice contribution to understanding observations of below-cloud wet scavenging and the need to remove air-mass changes. It deserves to be published. However, I have some comments that I’d like to be addressed. I’m particularly concerned about Figure 8 and its interpretation, and this is the focus of my last 4 comments.

The manuscript needs a general review of English (including title and throughout). Generally, the issues don’t prevent the points from being understood, but things can be cleaned up to make the manuscript a bit easier to read. As an example with the title, it would be more common to say, “The variation of the particle number size distribution during the rainfall: wet scavenging and air masses changing”

Section 2.2: The criteria listed here have somewhat arbitrarily chosen cutpoints. How sensitive are the results to changes in these cutpoints?

Figure 2: I found it hard to see the “theory” curve on the plot (the pink was very light), please make it darker or make it a line. 

Figure 2: What assumptions were made for the “theory” curve? The rainfall rate and the rain size distribution will affect this curve. Related, the rain conditions for each of the obs studies on the plot may different, so it’s worth discussing these potential differences.

L241-242: I don’t understand this statement. It might be because I’m not sure what a “backwards air mass” is (do you mean “back trajectory”?).

Figure 6: Is there a reason why type iv is not plotted here? Should mention why.

Figure 7: The CO change here seems like the most straightforward evidence of the airmass change, given that it’s a non-scavenged species. Not necessary, but this could be made more prominent in the paper (e.g., abstract, moving it forward in the results, etc.).

Figure 8: What size are these BWSC coefficients for? Is it for the total number of particles, regardless of their size? If true, this complicates the interpretation of the figure since there is likely a correlation between the particle number concentration and the size of the particles. I recommend instead making this plot for the BWSC for a specific size, which makes for a fairer comparison (or at least having this as a second panel). 

L327-329: It does not make physical sense that the BWSC depends on number concentration. Below-cloud wet scavenging is a 1st-order loss process, particles should not be influencing other particles’ ability to be scavenged. It seems much more likely that particle number and the average size of the particles are at least somewhat correlated, and that is driving the relationship here. This is why making Figure 8 show the BWSC for a specific size would be easier to interpret. (Also, is there a relationship between rain rate or the rain drop size distribution and the number of particles? A correlation here seems less likely than the relationship between particle number and particle size, but worth checking since it could also influence the interpretation of Figure 8.)

L341-342: How? Below-cloud wet scavenging  is a first-order process. It should not depend on the number. However, it does depend on particle size. See the two comments above. The interpretation here seems incorrect.

L342-344: Unless the particle concentrations are extremely high, below-cloud scavenging should be removing particle number much faster than coagulation.