基于CMORPH资料的长三角城市化对降水分布特征影响的观测研究

Urbanization effects on precipitation over the Yangtze River Delta based on CMORPH data

利用CMORPH卫星降水资料和NCEP风场资料,综合分析了长江三角洲地区南京、杭州、上海、苏州等主要城市的降水分布特征,结果表明:长三角城市效应主要表现在对夏半年降水强度空间分布的影响,具体表现为在700 hPa平均引导气流控制下,城市中心和下风向地区的夏半年降水强度比上风向地区增加5%～15%,最大值通常位于城市中心下游20～70 km。冬半年主要城市周围的降水量、降水时间和降水强度的空间变化都比较小,城市效应对降水分布特征没有明显的影响。长三角城市因地理位置的差异,不同城市降水的下游效应存在差别。夏半年南京、杭州、无锡、苏州、常州等城市的下风向地区比上风向地区降水强度明显增加,城市效应显著。上海和宁波受到海洋影响明显,夏半年低层海风侵入范围较广,夏季降水强度的高值中心偏向海风的下游方位,可能是受到海风环流和城市热岛环流的共同影响。距离上风城市较近的镇江等城市,降水强度的分布受到上风城市降水强度下游效应的影响。

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.