高原夏季风对中东亚干旱半干旱区夏季降水的影响

Influence of Plateau Summer Monsoon on Summer Precipitation in the Arid and Semi-Arid Regions of the Central and East Asia

通过比较7种再分析资料计算的高原夏季风指数,并分析了高原夏季风与中东亚干旱半干旱区夏季降水的关系,总体上7种再分析资料得到的高原夏季风指数是相当一致的,并且在滤去10年以上周期的长波后,7种再分析资料计算的高原夏季风指数之间的相关系数比滤波前都有一定程度的提高,说明再分析资料在描述高原夏季风年际变化时是一致的。相关分析和合成分析的结果表明,高原夏季风对中东亚干旱半干旱区的夏季降水变化有重要的影响。高原夏季风偏强时,中亚地区偏南风异常并伴有辐合,南疆地区为异常东风,有利于水汽输送到这一地区,降水偏多,华北地区为异常东北风,阻碍了西南气流水汽的输送,降水偏少;高原夏季风偏弱时,中亚地区为北风异常并伴有辐散,南疆地区为异常西风,降水偏少,华北地区为异常西南风,降水偏多。

The summer monsoon indexes in the Qinghai-Xizang Plateau derived from seven reanalysis datasets and their relationship with the summer precipitation in the arid and semi-arid regions of the Central and East Asia are examined in this study. Overall,the variations of plateau summer monsoon are fairly consistent among the seven reanalysis datasets,especially in interannual time scales. Correlation and composite analysis showed that the plateau summer monsoon plays an important role on variations of summer precipitation in the study region.During the strong plateau summer monsoon years,anomalous southerly winds with convergence in the Central Asia and anomalous easterly winds in southern Xinjiang bring more moisture transport to the study region,leading to more precipitation. While in Northern China,the anomalous northeasterly winds hinder the water vapor transport by the southwesterly flowand inhibit the precipitation development. During the weak plateau summer monsoon years,anomalous northerly winds with divergence in Central Asia and anomalous westerly winds in southern Xinjiang lead to less rainfall. While in Northern China,the abnormal southwest wind leads to excessive precipitation.