Abstract:Based on the CMORPH(CPC Morphing Technique) satellite rainfall data and wind data from the NCEP/NCAR reanalysis, the effects of urbanization on precipitation were analyzed in major cities over Yangtze River Delta. Results show that, in general, urbanization has a significant effect on the precipitation intensity in summer and autumn. The rainfall intensity increases over and downwind of major urban cities under the 700 hPa steering flow. The maximun value was generally found at a distance of 20-70 km downstream from the center of the city. There are little effects of urban on precipitation in spring and winter. Due to the geographical differences, the distribution of precipitation shows differences among urban cities. In summer and autumn, rainfall intensity was increased significantly downwind of Nanjing, Hangzhou and Suzhou and Changzhou. However, the rainfall center is located over the downstream of sea breeze circulation in Shanghai and Ningbo. The precipitation intensity is probably influenced by both sea breeze circulation and urban heat island effect together. It was also found that the rainfall intensity of Zhenjiang was deeply affected by upstream urbanization.