中文摘要：

青藏高原作为一个抬升的热源对亚洲季风演化及其周边区域降水都有着深刻影响，近年来高原春季冷暖异常引起学者们的高度关注。本文利用NCEP II和NOAA资料分析了近33年春季高原感热通量、东亚夏季风北缘及中国北方雨季降水年际年代际变化特征，进而利用公用大气模式CAM5进行了关闭春季高原感热的敏感性数值试验。主要结论如下：近33年来春季高原感热通量呈下降趋势，与中国北方雨季（7—8月）降水显著正相关，达到95%显著性水平。春季高原冷（2000—2011年，简称CTP）较暖时段（1986—1997年，简称WTP）感热通量平均降低20 W·m^-2左右。相应地，夏季风北缘平均南退3个纬度左右，导致中国北方雨季大气可降水和降水率也分别减少2.44 kg·m^-2和1.09 mm·d^-1。数值试验结果显示，当关闭春季（3月1日至5月15日）高原感热对大气加热时，东亚夏季风整体爆发时间明显推迟，夏季风最北位置偏南2-3个纬度，中国北方整体降水减弱。这种因春季高原热源异常引起大气环流的改变是中国北方雨季降水多寡的主要原因之一，可以作为中国北方区域雨季降水的关键因子。

英文摘要：

As an elevated heat source, Tibetan Plateau （TP） has a significant impact on the evolution of Asian monsoons and the surrounding precipitation. Particularly in recent years, the occurrence of spring thermal anomalies over TP has attracted significant attention from scholars. This study uses the NCEP-DOE Reanalysis II （NCEP II） and National Oceanic and Atmospheric Administration （NOAA） to analyze the changes of spring （March to May） surface sensible heat flux （SSHF） over TP, the inter-annual and inter-decadal variations of the North edge of the East Asian summer monsoon （NSM） and rainy season precipitation in North China within the past 33 years. Further, a numerical sensitivity experiment is conducted in which the SSHF is shut off over TP, employing the Common Atmospheric Model version 5 （CAM5）. The main conclusions are as follows： the SSHF over TP during 1979-2011 exhibits a downward trend and has a significant positive correlation （at 95% significance level） with the rainy season （July-August） precipitation in North China. The averaged SSHF in spring decreases -20 W·m·2 during the cold （2000-2011, CTP for short） than warm time period （1986-1997, WTP for short） over TP. Correspondingly, the north margin of East Asia summer monsoon （NSM） retreats southward by an average of 3 degrees of latitude, causes the rainy season atmospheric precipitation and precipitable water in North China to decrease by 1.09mm·d^-1 and 2.44 kg·m^-2, respectively. The results of the numerical experiments indicate when the SSHF over TP is closed in spring （March 1st to May 15th）, the time of the EASM onset significantly delays, the NSM retreats southward by 2-3 degrees of latitude, and the rainy season precipitation in North China reduces by 1 mm·d^-1. The change in atmospheric circulation caused by the spring sensible heat anomaly over TP is one of the main causes of the rainy season precipitation in North China, and can be used as a key factor.