MAX-DOAS observations and their application to the validation of satellite and model data in Wuxi, China

Abstract:

Thomas Wagner¹, Pinhua Xie², Nicolas Theys3, Isabelle De Smedt³, MariLiza Koukouli⁴, Trissevgeni Stavrakou³, Steffen Beirle¹, Ang Li²,

1) Satellite group, Max Planck institute for Chemistry, Mainz, Germany

2) Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, China

3) BIRA-IASB, Brussels, Belgium

4) Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Greece

From 2011 to 2014 a MAX-DOAS instrument developed by the Anhui Institute of Optics and Fine Mechanics institute is operated in Wuxi, China, which is locatd about 100 km west of Shanghai. We determine the tropospheric vertical column densities (VCDs), near surface concentrations and vertical profiles of aerosols, NO₂, SO₂, HCHO from the MAX-DOAS observations using the optimal estimation profile retrieval algorithm (refered to as “PriAM”). We verified the results by comparing them with results from independent techniques, such as sun photometer (AERONET), a visibility meter and a long-path DOAS instrument. We acquire the cloud and aerosol conditions using a cloud classification scheme based on the MAX-DOAS observations (Wang et al., AMTD, 2015). Based on the obtained results, we characterize the effect of the clouds on the trace gas and aerosol profiles retrieved from MAX-DOAS. Then we characterize the diurnal, annual and weekly variations of the trace gases and aerosols and validate the tropospheric trace gas VCDs derived from the Ozone Monitoring instrument (OMI) on the Aura satellite platform as well as the model results from the IMAGES, CHIMERE and Lotos-Euros models and analyse the agreement depending on the cloud and aerosol conditions. Besides the direct comparison with the satellite data, we also use the trace gas and aerosol profiles derived from MAX-DOAS to recalculate the air mass factor (AMF) for the satellite observations and to evaluate the corresponding improvement of the satellite VCDs. In some periods with strong aerosol pollution, we evaluate the effect of the aerosols on the satellite cloud retrievals and the corresponding errors of the tropospheric AMF of the trace gases. Here should be noted that aerosol effects on the AMF is not yet considered in the published satellite products, which can cause appreciable errors of the tropospheric VCD of satellite products around polluted regions.