Abstract: Based on the method of multi-axis differential optical absorption spectroscopy (MAX-DOAS) retrieval of NO2 vertical column density (VCD), the corresponding ground-based MAX-DOAS system was constructed and the variation characteristics of NO2 VCD were observed. In the retrieval, the spectrum in the zenith direction was selected as the reference spectrum, and the NO2 slant column density (SCD) was retrieved by nonlinear least square method. Combining the slant column density of different observing directions, the NO2 differential slant column density (dSCD) was evaluated. Then the air mass factor (AMF) was calculated by the geometric approximation method, and finally the NO2 VCD was obtained. A one-year field experiment was carried out in Huaibei area from June 2019 to May 2020. The results showed that the monthly mean value of NO2 VCD presents an inverted “U” type change during the observation period, reaching the highest value of 2.13×1016 molecules·cm−2 in December and the lowest value of 5.23×1015 molecules·cm−2 in August. Moreover, the daily mean values of MAX-DOAS observations were compared with OMI (0 < FeC ≤ 0.1 and 0 < FeC ≤ 0.3) measurements, and it is found that the two results had a good agreement (R2 = 0.88, R2 = 0.90), which indicates that MAX-DOAS can not only accurately retrieve NO2 VCD, but also be used to verify the satellite data.

Key words: multi-axis differential optical absorption spectroscopy, OMI, NO2 vertical column density, contrastive analysis