|The authors have made an excellent job both in addressing and replying both reviewers' comments as well as altering their manuscript to now better demonstrate the status of air quality over East China. I highly commend them on that. Having said that, I am still concerned about the presentation of their findings. |
1. I would expect to first see the back-in-time discussion for the NO2 levels, i.e. Section 3.1.2, on OMI, and then what happened during 2020 and COVID, by TROPOMI, i.e. Section 3.1.1. It makes more of a natural flow of information this way, especially since you do not have back-in-time analysis for the AQI/surface concentrations.
2. Figure 4 shows OMI NO2 up to and including months of year 2020, these should be excluded since you do not plan to discuss them. Overall the quality of the graph is poor, make sure all labels increase in size, are made bold, and so on.
Furthermore, when a trend is calculated from such a seasonally-varying species as is NO2, the time series has to be de-seasonalised beforehand. This is not explicitly mentioned in the text. I strongly suggest that you first de-seasonalise and then provide trends in the relevant Table.
3. Since in the rest of the text you show weekly timeseries for the AQI/surface concentrations for the COVID weeks, I strongly recommend you also show, in the TROPOMI section, similar timeseries. If not, again your results appear to be "un-connected' i.e. you first have one satellite giving you the 10 year NO2 trend, then another giving you what went on during COVID for the 2020 weeks, then you have surface concentrations of NO2 and other species, plus AQI, only for the COVID 2020 weeks. I am not suggesting that you compare TROPOMI NO2 to the surface concentrations, this task is a paper on its own. You should however show if similar patterns appear. These patterns cannot be seen from Fig. 3 & Fig A1 which are demonstrational only.
Overall, from the time series provided, I note that the AQI is mostly influenced by PM2.5, rather than the variation on NO2.
Technical: throughout the text there are references to a Figure/Table in the supplement, I assume this was a typo error? Figure A1 should be made with a colour bar the reflects differences, i.e. going from blue to white -which means 0- and then to red. Figure A2 is of low quality and should be improved.