Abstract:The urbanization effects on precipitation over the Pearl River Delta area based on TRMM2A25 and CMORPH data are studied. It is found that the Pearl River Delta area is a rainfall centre where there is less precipitation than its surrounding area, especially for convective rainfall, and over the centre cities the rainfall tends to decline in the last ten years. It is suggested that the urbanization may result in the decrease in precipitation over the Pearl River Delta area. Furthermore, numerical experiments with WRF prove that the urbanization has a significant impact on the rainfall. One important interaction mechanism is also revealed, that is, the urban expansion reduces natural vegetation cover, and then it can help to decrease ground evaporation and local water vapor supply, enlarge surface sensible heat flux, deepen PBL height and enhance the mixing of water vapor. Hence it is not conducive to the occurrence of the rainfall