Spatio-temporal distribution of tropospheric NO2 and quantitative analysis of its impact factors over Yangtze Delta based on OMI satellite measurements

The characteristics of spatio-temporal distribution of tropospheric NO₂ vertical column density (VCD) over Yangtze Delta(YD) are presented, on the basis of measurements from the satellite instruments Ozone Monitoring Instrument(OMI). From these observations, monthly and yearly averaged tropospheric NO₂ variations are determined for the period of 2005-2009. A linear regressed model is used to fit the yearly variation series of tropospheric NO₂ from 2005-2009 over YD, accordingly the annual changes in tropospheric NO₂ is obtained. The relativity between the NO₂ vertical column density and its influencing factors such as population density, vehicles amount, gross industrial production and annual power consumption are quantitatively evaluated by correlation analysis. The results show the heavy pollution of NO₂ is mainly distributed in the main economic zone. The central axis of the main economic zone is a polyline whose nodes are Nanjing, Shanghai and Hangzhou. The average tropospheric NO₂ VCD over the main economic zone is about 1928×10¹³ molec/cm², which is about double twice to the remaining parts of YD. The temporal variation of the NO₂ VCD above the entire YD area is relatively slow in recent 5 years, about 3.5% a^-1. The small growth rate may result from the economic crisis in 2008 and changes in industrial structure in the Yangtze Delta. Correlation analysis results show that the NO₂ over the Yangtze Delta is firstly influenced by the vehicles population, indicating vehicle emissions plays a most important part in the NO₂ pollution over YD in recent years.