西北西部夏季干湿年的水汽输送特征

利用1961—2007年NCEP/NCAR逐月再分析资料和中国地面气候资料国际交换站数据集台站降水距平百分率资料,分析了西北西部干、湿年夏季的水汽输送差异。结果表明,北疆偏湿润年,在对流层中、低层有一支源于阿拉伯海的异常水汽输送通道,它向西北方向流经波斯湾后折向东北方向流入北疆,这是热带海洋水汽输送进入北疆的最短路径。南疆—河西走廊西部偏湿润年,异常水汽通道主要是位于对流层中、低层的一支源于北方的水汽输送带,它作反气旋式运动后以偏东气流的形式流入河西走廊西部及南疆,由于该水汽输送源自北方,水汽含量小,这可能是造成该地域极度干旱的直接原因之一;另一支更弱的异常水汽通道位于对流层高层,它源自阿拉伯海,流经印度半岛后折向北,越过青藏高原后进入南疆。

CHARACTERISTICS OF MOISTURE TRANSPORTATION IN WET/DRY SUMMERS IN WESTERN NORTHWEST CHINA

The station rainfall departure percentage data and NCEP/NCAR reanalysis data for the period of 1961--2007 are employed to discuss the moisture transportation differences between dry and wet summers in the west part of NW China. It is shown that, during wet summers in Northern Xinjiang, a channel of moisture transportation exists at mid-lower levels from the Arabian Sea, which goes northwestward across Persia Gulf and then turns southeastward into Northern Xinjiang. It forms the shortcut of water vapor from the tropical ocean into Northern Xinjiang. Meanwhile, during wet summers in Southern Xinjiang and Western Hexi Corridor, the moisture channel is mostly located at the high latitudes of mid-lower levels, which moves anticyclonically and flows into Southern Xinjiang and Western Hexi Corridor. Since this moisture transportation is from south with small water vapor content, it probably is one of the direct reasons that cause the extreme drought in the region. Another even weaker moisture transportation channel is at high level from Arabian Sea, which turns northward after flowing across Indian Peninsula and then climbs over the Tibetan Plateau to enter Southern Xinjiang