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 AOT₅₅₀ was in good agreement with data obtained from four ground-based AERONET sunphotometers (R>;0.89). AOT₅₅₀ over main big cities increased gradually year by year. Seasonal variation analysis of AOT₅₅₀ 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 AOT₅₅₀ over the plain cities is larger than those over the mountainous area cities. Decrease in AOT₅₅₀ over Shanghai during the World Expo was primarily was found, the reason was attributed to the reduction in coarse mode aerosol particles.