珠江三角洲城市群对夏季降雨影响的初步研究

摘要

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%利用TRMM 2A25卫星降水数据和CMORPH同化数据对珠三角洲地区的降水分布特征进行了探讨,观测表明:珠三角城市群区域总体处于降水的低值中心,且对流降雨的低值中心尤为明显；同时近10 a珠三角核心城市区域降雨有减少的趋势,这种降水减少的趋势可能与珠三角城市化效应有关.本文进一步利用WRF模式模拟分析了珠三角城市群发展对夏季降雨的影响,结果表明珠三角城市化使得该区域降雨减少,其原因为城市化使得地表的蒸发减弱及其大气中的水分供应减少,同时也抬升了珠三角区域边界层高度相应增强了低层大气水汽垂直混合.