浙江省汛期旱涝趋势对气候变暖的响应

Trends of drought and flood in Zhejiang Province respond to climatic warming.

近50多年来浙江省气候变化总趋势在逐渐变暖,80年代中期开始变暖明显,增幅加大.浙江省汛期各月降水量对气候变暖的响应不同:在季节转换月份5月和9月,降水量明显减小,而在夏季的降水量增加,8月尤甚.在气候变暖期,浙江省汛期旱涝事件的发生频数增加.大气环流对气候变暖的响应是:5月份,高层南亚高压偏弱偏南,中国东南部上空为平直的西风气流,引导冷空气多偏北东移,中层印缅槽的减弱导致向江南水汽输送减少,低层偏南气流远离华东,浙江省主要受单一西北干燥气流影响,降水显著偏少;8月份,青藏高压位置偏西,中国东南部上空西北气流有利引导冷空气南下,低层越赤道气流加强了赤道幅合带的扰动,有利台风的生成和发展,中层副高南侧偏东气流有利于引导台风北上登陆华东,导致影响浙江台风年频数增加,台风与冷空气相互作用有利强降水发生,形成台涝.在气候变暖期海水表层温度距平升高,ENSO事件的多发、增强的倾向影响了浙江省汛期旱涝趋势.

Trends of climatic variability during climatic warming in Zhejiang Province have been analyzed. Month rainfull reduced in May and September, and increased in June, July and August. Annual frequecies of drought and flood events increased. There were less rainfall in May because South Asia high was weaker and southwarder, cold air were eastward steered by zonal westerlies, and less water vapour was transported to southeast China. There were more rainfall in August because Tibetan high was located westwarder, and cold air was southward steered, and disturbances were activated in ITCZ by cross-equatorlal flow, and more tropical cyclones generated and developed, and there were more landfall on southeast China by steering of Apheliotes, so that annual frequencies of Tropical Cyclone effecting Zhejiang increased. During climatic warming SSTA rose, and there were so severeler ENSO that trends of drought and flood were more.