青藏高原汛期降水异常空间分布及水汽配置

Spatial patterns and moisture configurations of rainfall anomalies in flood season over the Tibetan Plateau

青藏高原汛期(5—9月)降水具有南北反相的空间分布特征,利用青藏高原67个台站1967—2008年逐月降水资料,分别讨论了汛期各月降水的主要空间分布型以及初夏(5—6月)和盛夏(7—8月)对应的水汽配置和环流异常。结果表明:初夏高原降水以南北反相型(North-South Reverse Type,NSRT)为主,全区一致型(Whole Region Consistent Type,WRCT)次之;盛夏高原降水以WRCT为主。高原降水呈现NSRT分布时,初夏水汽由高原南部输向北部,而盛夏高原北部为水汽辐合区,南部为水汽辐散区。高原降水呈现WRCT分布时,初夏高原水汽主要来自西太平洋,盛夏水汽主要来自阿拉伯海向东转向的水汽输送,该水汽输送由高原西南地区进入高原。在500 h Pa位势高度场上,初夏(盛夏)降水两种主要空间分布型的位势高度差异以经(纬)向差异为主,且影响高原降水异常分布的系统多为深厚系统。

There is a north-south reverse pattern in precipitation in flood season（May to September） over the Tibetan Plateau.Based on the monthly rainfall data of 67 stations over the plateau from 1967 to 2008, this paper studies the principal spatial patterns of monthly rainfall during the flood season, and the moisture configurations and circulation anomalies in the early summer（ May to June） and midsummer （July to August）, respectively.It is found that there are two main patterns in summer, but they are different between the early summer and midsummer. The former has an advantage in north-south reverse type （NSRT）, while the latter exceeds in whole region consistent type （WRCT）. When the rainfall shows NSRT, the moisture transport comes from south to north Tibetan Plateau in the early summer, and the convergence （divergence） of water vapor locates in north （south） Tibetan Plateau in the midsummer.While the rainfall shows WRCT, the moisture transport comes from western Pacific in the early summer. In the midsummer, it comes from the eastward ransport of water vapor from Arabian Sea, which enters the plateau from its southwest areas.At 500 hPa, the meridional（zonal） geopotential height differences between the two patterns are predominant in the early summer（ midsummer）, and the circulation systems impacting distributions of precipitation anomalies are mostly deep.