青藏高原对1998年长江流域天气异常的影响

利用NCEP再分析资料分析了青藏高原对 1998年夏季长江流域洪涝及天气异常的影响 ,并讨论了第 2段梅雨期的暴雨与长江流域洪涝灾害的关系。研究结果表明 :由于青藏高原的热力作用 ,夏季高原东北部斜压性强 ,多短波槽活动。 1998年长江流域两段梅雨期间 ,高原东移的短波槽加强了梅雨锋 ,并引起梅雨锋上强暴雨。 1998年长江流域的 8次洪峰均与高原东侧短波槽东移有关。由于梅雨期前面几场暴雨已使得土壤水份饱和 ,沿江各支流及湖泊水位很高 ,梅雨期的最后一场暴雨的大量雨水往往作为径流流入江河或湖泊 ,与长江洪峰汇合后易造成洪涝灾害

THE INFLUENCES OF TIBETAN PLATEAU ON WEATHER ANOMALIES OVER CHANGJIANG RIVER IN 1998

The influences of the Tibetan Plateau on weather anomalies over the Changjiang River in 1998 are studied by analyzing the NCEP reanalysis data . There are many short wave troughs over the baroclinic zone ,northeast part of Tibetan Plateau, associated with its thermal effects. The short wave troughs pass through the Meiyu frontal zones and reinforce them, finally cause the heavy rainfall. The 8 flood peaks in middle reaches of the Changjiang River are caused by short wave troughs moving eastward. The relation between the heavy rainfall during the second period of Meiyu rainfall and the severe flood is also discussed. Several heavy rainfalls prior to the last one saturated soil moisture, So the severe floods are easily followed the last heavy rainfall which offered a chance for confluence of high stage waters from the upper reaches of the Changjiang River and from the Dongting and Boyang Lakes.