近30 a青藏高原夏季空中水资源时空变化特征及其成因

综合考虑高原大地形以及南亚季风、中纬西风带的影响，利用1979-2010 年NCEP/NCAR再分析资料，从高原整体空中水资源分布以及区域可降水量与水汽收支变化等方面剖析了青藏高原夏季（6-8 月）空中水资源时空变化特征及其机制。分析表明：除高原西北部外，其它4 个分区多年平均水汽净收支为汇。1979-2010 年，高原中南、东南与西北部可降水量与水汽净收支均呈递减趋势，东北部相反，中北部水汽净输入减弱但可降水量增加。高原空中水资源变化与中纬西风带和南亚季风水汽输送关联密切，区域西风、南亚季风活动减弱分别反映了高原中东部纬向水汽、30°N以南经向水汽输送的减少；而高原特有的地形分布加剧了各分区水汽净收支变化格局。

Characteristics of Summer Atmospheric Water Resources and Its Causes over the Tibetan Plateau in Recent 30 Years

Considering the effects of unique landscape of the Tibetan Plateau (TP), South Asian monsoon and mid-latitudes westerlies, the spatiotemporal variation of the summer atmospheric water resources and its main causes over the TP are analyzed from the aspects of the precipitable water content, the water vapor transport and budget with the adoption of NCEP/NCAR monthly reanalysis data from 1979 to 2010. The results show that the 32-year regional mean water vapor net budgets were convergences for the whole TP but the northwestern part. The precipitable water vapor and water vapor budget over the south-central, southeastern and northwestern TP exhibited increasing trends, while the northeastern TP decreased during the period of 1979-2010. Despite of the rising of precipitable water vapor, the water vapor net income declined over the north-central TP. The mid-latitude westerlies and South Asian monsoon dominated the variability of atmospheric water resources over the TP, and the interdecadal descending characteristics of the zonal index and the South Asian monsoon index implied the weakening of the zonal moisture transport over the east-central TP and meridional transport over the south of 30°N in the TP and its surrondings, respectively. Moreover, the difference of the water vapor budget among the five partitions was exacerbated by the unique landform distribution of the TP.