Spatial-temporal variability of aerosol optical depth over the Yangtze Delta during 2001–2008

Aerosol optical thickness is a principal indicator to describe the atmospheric condition and the effect of aerosols on radiative transfer in the earth's atmosphere. In this study, the distribution and seasonal variation trends of AOT over the Yangtze Delta during 2001–2008 and World Expo were studied. The results show that the MODIS AOT 550 was in good agreement with data obtained from four ground-based AERONET sunphotometers (R>0.89). AOT 550 over main big cities increased gradually year by year. Seasonal variation analysis of AOT 550 revealed peak values over the cities in plain regions appear in summer but those over the cities in mountainous areas appear in spring. The yearly increasing trend of AOT 550 over the plain cities is larger than those over the mountainous area cities. Decrease in AOT 550 over Shanghai during the World Expo was primarily was found, the reason was attributed to the reduction in coarse mode aerosol particles.