Characteristics of Aerosol Optical Thickness as Well as the Relationship with NDVI in the Yangtze River Delta, China

Abstract

A long term (2000 - 2008) dataset of aerosol products retrieved from MODerate Resolution Imaging Spectroradiometer (MODIS) is used to investigate the temporal and spatial variations of aerosol optical thickness (AOT) over the Yangtze River Delta (YRD). Ground-based observations (sun photometers) were used to validate the MODIS L2 aerosol products, and the Normalized Difference Vegetation Index (NDVI) derived from SPOT-VGT is used to analyze the relationship with AOT. The results illustrate that the highest correlation (R = 0.92) of CE-318 AOT vs. MODIS AOT is in Hangzhou with the slope and intercept of 1.04 and -0.01. The largest value of AOT appears in June, and has the largest spatial differences in July. There are two different aerosol patterns. One includes smaller AOT over dense vegetation cover areas dominated by natural aerosols and the other involves larger AOT over urban areas where anthropogenic aerosols dominate. The correlation analysis indicates that there are moderate negative correlation coefficients (R) for AOT vs. NDVI, and the R values vary as seasons shift. The range of R values is 0 ~ -0.8 and the mean values are about -0.5. The relationship between AOT and NDVI is more obvious in dense vegetation areas.