近50年华北干旱的年代际和年际变化及大气环流特征

The Decadal and Interannual Variations of Drought in the Northern China and Association with the Circulations

利用 1 948～ 2 0 0 0年NCEP/NCAR再分析逐日及月平均位势高度、风、温度、垂直速度等物理量和中国气温、降水资料 ,分析近 50年中国华北地区干旱的年代际、年际变化及其环流特征 ,并探讨 1 999和 2 0 0 0年华北地区持续干旱环流型及其成因。研究指出 :2 0世纪 80年代以来华北地区降水持续偏少 ,干旱强度有所增加 ,这与夏季 2 0 0hPa矢量风距平场亚洲中纬度西风环流加强 ,850hPa风矢量距平场中国东部 1 1 0～ 1 2 0 oE范围内偏南气流比气候平均状况偏弱有关。夏季华北降水偏少的一种主要大气环流型是 :50 0hPa位势高度场上 40～ 50 oN的欧亚大陆位势高度偏高并叠加欧亚 (EU)遥相关型 ,华北大部分地区受高压控制。 1 999和 2 0 0 0年夏华北地区持续严重干旱的主要环流特征是 :亚洲大陆高压持续发展、长期维持并相当稳定 ,华北地区上空受闭合暖性高压控制 ,高空暖性高压气流强烈下沉 ,引起空气绝热增温 ,近地面感热增加使得干旱区气温升高 ,下垫面非绝热强迫作用与大陆暖高压加强形成正反馈过程。

A study of the decadal and interannual variations of drought in the northern China during summer is presented. There were a plentiful rainfall during 1951～1964 and a less rainfall during 1980～1997.The decadal drought pattern during 1980～1997 at 500 hPa was that the anomalous height in middle latitude over Eurasia continent were above normal. There were total different wind anomalous patterns at 200 hPa and 850 hPa between during the period of 1950～1965 and 1980～1997. The pattern of the typical drought year over the northern China was there was the teleconnect pattern over Eurasia continent (EU pattern) at 500 hPa which means the anticyclone occupied in the northern China. The main character for drought in the northern China during 1999～2000 was that the positive anomalous height in the middle latitude of Eurasia continent at 500 hPa jointed EU pattern.