Please find the comments in the attached PDF file.

The authors directly measured the uptake coefficient of N2O5 using an aerosol flow tube reactor in Kumin, a highland environment, in China. The possible influence factors on the γ(N₂O₅) were discussed by correlation analysis in this work. ALWC was the most important one affecting the measured γ(N₂O₅). The comparison between the measured γ(N₂O₅) and parameterized values. Overall, the results are well presented and discussed. It is publishable after the following questions have been well addressed.

1. Considering many studies on the γ(N₂O₅) by measurement, modeling, and parameterization methods, I am wondering what scientific assumption is focused on in this work. The uptake kinetics in different environments? Crucial factors determining the γ(N₂O₅)? Or the uncertainties of the parameterization method for γ(N₂O₅)? The authors should clarify the highlights and the novelty of this study.
2. It is somewhat too weak about the correlation analysis between the measured γ(N₂O₅) and possible factors such as chemical composition and ALWC. The dataset is too small and the data points are too scattering. So, it is hard to observe the significant correlation.
3. About the negative correlation between organic aerosol and γ(N₂O₅), is the γ(N₂O₅) possibly affected by other factors when the concentration of organic is high along with a low γ(N₂O₅)? Unless organic aerosol is well mixed with other components, i.e., in an ideal inner mixed state.
4. ALWC is the most important factor affecting γ(N₂O₅). However, ALWC is greatly determined by nitrate concentration or fraction in PM2.5. Why does γ(N₂O₅) show a different dependence on nitrate like ALWC?
5. In Figure 2b, it is better to compare the γ(N₂O₅) distribution among different methods.
6. In Figure 4, the performances of these parameterization methods look too bad. I am wondering how about the performances of models widely used in literature.