Dear Dr. Drosoglou,

I have received the recommendations from the two referees. One of them still has a few questions and suggests further revisions of the manuscript. Please consider the comments from this referee carefully and give a proper response.

I also have a question as below.

In page 13, line 22-24, you state that the use of actual satellite geometry for each day is complex and would require a much larger domain for the air-quality simulations, more than double the currently used (120 km×120 km) in order to include all possible pixel sizes and positions for each location. It is difficult for me to understand this statement as you have mentioned (in page 11, line 26-29) that the OMI sensor provides better detection of higher local pollution levels [Kramer et al., 2008], due to its higher spatial resolution (13 km × 24 km at nadir), compared to GOME-2 sensors which detect the average NO2 concentration over a larger area (40 km × 40 km for MetOpA and 80 km × 40 km for MetOpB). Should some outmost pixels at the swath edges be discarded or not when making a comparison with model simulations?

Please also consider the following technical issues when making a revision of your manuscript.

Page 1, line 22: Change “resulted to” to “resulted in”.

Page 1, line 23: Change “Phaethon” to “MAX-DOAS”.

Page 2, line 29: Change “date back in” to “date back to”.

Page 3, line 31: what is the meaning of OH here?

Page 4, line 14 and line 16: Change “has been operating” to “was operated”.

Page 4, line 33, “Fig. 2”: Please renumber the figure in Page 30 (change “Figure. 3” to “Figure 2”) and move it to the previous page, just after Figure 1.

Page 5, line 28, “Fig. 4”: Fig. 3 has not been mentioned before. Please change “Fig. 4” here to “Fig. 3”, renumber the figure in Page 31 (change Figure 4” to “Figure 3”) and move it to the previous page, just after the updated Figure 2.

Page 5, line 31, “Fig. 2”: Please change “Fig. 2” here to “Fig. 4”, renumber the figure in Page 29 (change Figure 2” to “Figure 4”) and move it to the back page, just after the updated Figure 3.

Page 5, line 31,Table 2: “Table 1” should have appeared somewhere in the text before.

Page 14, line 7: Change “all three instruments” to “all three satellite instruments”.

Please do not hesitate to contact me if there is something unclear.

Sincerely,
Jianzhong Ma

Dear Dr. Drosoglou,
The accepted manuscript are generally sent to the editorial office for language editing before publication. Your manuscript can be polished by rephrasing some expressions in English. For example, the first sentence in the last paragraph of the Sect. 4 (line 4-5, page 16) might be changed to“In the present study, only a relatively short period of the data set from the MAX-DOAS measurements has been used for the validation of the satellite observations due to technical issues that arose during the campaign”.
Sincerely,
Jianzhong Ma