山东雨季季内降水分型及旱涝并存与急转——气候特征

INTRASEASONAL PRECIPITATION PATTERNS AND COEXISTENCE OF DROUGHTS AND FLOODS AND ABRUPT ALTERNATION IN SHANDONG PROVINCE IN RAINY SEASONS ——Climatology

采用1965—2007年山东省地面测站的逐日降水量和同期NCEP日平均再分析资料,运用统计学方法,探讨了季内降水分型、季节内振荡及旱涝突变的气候特征。结果表明,主要分为全省一致Ⅰ、东西反相Ⅱ、南北反相Ⅲ三种类型。他们的季内旱涝急转显示了典型的气候意义,Ⅰ型在6月下旬旱涝急转、8月中旬后期和9月初涝旱急转,与山东"夏季"雨季开始、结束时间的关键期是一致的。分型不仅限于山东,而是有着更广的旱涝区域。当Ⅰ型正相位时500 hPa高度场对应亚欧-北太平洋中高纬度为正距平,Ⅱ型表现出西北太平洋西岸的PJ波列,Ⅲ型对应着从西太沿岸-美洲西岸的类PNA型遥相关。

Daily precipitation data from Shandong observattories and NCEP reanalysis daily data for the period of 1965—2007 were used to conduct statistical estimation of the intra-seasonal precipitation types and coexistence of droughts and floods and abrupt alternations.The results indicate that intraseasonal precipitation types include spatial patterns of I total consistency,II east-west out-of-phase,and III north-south out-of-phase,in which the latter two types reflect spatial coexistence of droughts and floods.Type I has 30-60 d rhythms in summer half years,but type II and III have quasi-one-week and quasi-two-week oscillations,which are significant in July and August.Representative climatic events were revealed in abrupt alternations of droughts and floods for all of the three climatological types.Abrupt droughts-floods alternations in late June,late mid-August and in early September respectively correspond to the key dates of onset and end of summer monsoon precipitation.The precipitation types spread to regions outside Shandong Province,contributing to a large-scale anomalous general circulation.When Type I is positive,positive anomalies at 500-hPa geopotential heights appear in the mid-high latitudes from the Eurasia to the North Pacific.Type II exhibits PJ wave train along the west coast of Northwestern Pacific,and Type III displays a quasi-PNA teleconnection pattern from Northwestern Pacific coast to the west coast of America.