近50年珠江流域降水时空特征分析

Analysis of spatial and temporal distributions of rainfall in Zhujiang river basin in the past 50 a

为了更深入揭示珠江流域水资源状况,利用珠江流域内1961—2008年48个台站逐日降水资料,探讨了珠江流域年降水时空特征,并对典型年份的气候背景场进行了分析。结论表明:相对来说,珠江流域东部年均降水多而降水日数少,西部一些地区降水量少而降水日数较多,从总体上来看近10 a来流域内年降水总量波动较大。进一步讨论了珠江流域典型降水年份中降水事件的差异,发现强降水年的降水量多来自于大雨以上级别的强降水。从全年来看,强降水年有来自于孟加拉湾和南海异常的偏南风水汽输送,流域内并伴随有异常水汽辐合中心;弱降水年则水汽输送减弱,且存在水汽辐散中心;由于年降水总量近80%来自于夏半年(4—9月),登陆到流域内热带气旋偏多也是导致降水增加的原因之一,登陆的热带气旋主要来自于西北太平洋;夏半年西太平洋副热带高压偏西有利于把海上的水汽送到流域内,弱降水年则恰好相反。

By using the daily precipitation data from 48 meteorological stations in Zhujiang basin from 1961 to 2008, the temporal and spatial characteristics of precipitation were discussed and mecha- nism in typical years was analyzed. Analysis results showed that precipitation amount is plentiful, but day numbers is small in the east of Zhujiang basin, while the west is contrary. On the whole, precipitation is changeable in recent 10 a. Moreover, the difference of typical rainy years is further discussed. It was found that the heavy typical years are always caused by heavy rainfall. In heavy precipitation years, en- riched vapor transport comes from bay of Bengal and South China Sea;the summedy precipitation makes a greater contribution to the yearly precipitation; more tropical cyclones make landfall in the basin and they mainly come from the Western Pacific, causing heavy precipitation; the summerly west position of Pacific subtropical high helps to transport water vapor to basin from the Pacific, but it is contrary in weak years.