The seasonal correlation between atmospheric water vapor and aerosol extinction and the relationship between aerosol, NO2, SO2 and water vapor during haze pollution in Qingdao, China

MAX-DOAS observations was carried out from March 1, 2019 to December 31, 2019 in Qingdao, China, to measure the O₄, NO₂, SO₂ and H₂O absorption, to retrieve AOD and the troposphere vertical column concentration of NO₂, SO₂ and H₂O.We use PriAM algorithm which based on the optimal estimation to calculating volume mixing ratio profile of trace gases, aerosol and water vapor during 0 ~ 4 km. The correlation between AOD and H₂O VCD was analyzed in every month, the results showed that the AOD and H₂O VCD has good linear relationship in each month., illustrate the increase of water vapor concentration will lead to the increase of moisture absorption of aerosol. The seasonal variation of the four seasonal correlation slopes in the order of summer < autumn < spring < winter. The influence of concentration change of NO₂ VCD, SO₂ VCD, H₂O VCD and AOD is discussed in a haze episodes occurred in December 2019. Discovery that the H₂O VCD and AOD was increased at the same time in the haze pollution incident, but with the increase of water vapor concentration, the concentration of NO₂ and SO₂ decreases, indicated that due to the increase of concentration of water vapor, NO₂ and SO₂ heterogeneous reaction will happen to generate nitrate and sulfate aerosols, so that the concentration of NO₂ and SO₂ concentration was decreased. The relationship between NO₂, SO₂, AOD and water vapor mixing ratio of 50m, 200m, 400m and 600m during haze pollution period was also studied, and it was indicated that phenomenon aerosol extinction increased with the increase of water vapor mixing ratio, while NO₂ and SO₂, on the contrary, were more obvious at 50m and 200m near the ground.