Intercomparison of slant column measurements of NO2 by ground-based MAX-DOAS

Abstract

In September 2011, we used 3 ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) instruments of different designs and operation protocols to measure tropospheric NO2 for about 20 days, at the Station of Atmospheric Comprehensive Observatory, Institute of Atmospheric Physics, Chinese Academy of Sciences (Xianghe 117.0N, 39.77E). All instruments are oriented to an azimuth angle of 270 (north), in a common wavelength range and with a set of cross sections for the inversion of NO2 slant column in visible and UV wavelength range respectively. Intercomparison of NO2 slant columns among three MAX-DOAS is introduced. The results obtained from the different instruments are in good accordance with each other, and the correlation coefficients are all higher than 0.95, but systematical errors exist. Daily average errors of three MAX-DOAS instruments are almost below 6%, showing that the instruments work steadily and the data are cogent. The UV results are smaller than those in the visible range, especially on the overcast days, related to the wavelength dependence of Rayleigh and Mie scattering. After the correction of systematical errors, there is better consistency among different results, which indicates that the three MAX-DOAS instruments have a capability to validate the atmospheric component products of satellite.