夏季青藏高原对流层温度与西北太平洋副热带地区降水的关系

利用1979-2016年CMAP(CPC Merged Analysis of Precipitation)和GPCP(Global Precipitation Climatology Project)的降水数据以及ERA-Interim再分析资料,通过统计方法研究了夏季青藏高原地区对流层中上层温度年际变率与同期西北太平洋副热带地区降水的关系及其相关的物理过程。结果表明,在年际变化尺度上,夏季高原对流层温度与同期西北太平洋副热带地区降水存在显著的正相关,即当高原对流层温度偏高时,西北太平洋副热带区域的降水偏多,反之亦然。分析研究指出,当夏季高原对流层温度偏高时,高原上空南亚高压显著增强并且向东扩展至日本地区,高原北部对流层出现异常的上升运动,这一异常上升气流随着高度增加逐渐北偏,并在中高纬度地区沿着异常西风气流向东扩展至日本地区,随后向南下沉至日本南部;受该异常下沉运动影响,日本南部对流层低层出现异常反气旋,其东侧的异常北风与西北太平洋低层的异常气旋、反气旋环流存在紧密联系。西北太平洋地区这种异常环流特征为西北太平洋副热带区域的降水提供了有利的动力和水汽条件,从而使该区域降水增多。

Relationship between Tropospheric Temperature over Tibetan Plateau and Precipitation in Subtropical Western North Pacific in Summer

Based on the CMAP and GPCP precipitation data and the ERA Interim reanalysis data during 1979-2016, this study examines the relationship between mid upper tropospheric temperature in the Tibetan Plateau (TP) and precipitation in the subtropical western North Pacific (WNP) during boreal summer and analyzes the associated physical processes. The results show a significant positive correlation between the TP mid upper tropospheric temperature and the subtropical WNP precipitation on the interannual scale. When temperature in the mid upper troposphere is high over the TP, the South Asian high is significantly enhanced and extends eastward to Japan. Meanwhile, there is an anomalous upward flow in the northern TP, and it gradually shifts northward with height, expanding eastward to Japan along anomalous westerly winds to the north of the enhanced South Asian high and moving downward in the area south of Japan. Corresponding to the anomalous downward motion to the south of Japan, there is a lower troposphere anomalous anticyclonic circulation in the southern Japan, with the northerly wind anomalies to the east of the anomalous anticyclonic circulation, which is closely related to the anomalous cyclonic anticyclonic circulation coupling structure in the lower tropospheric WNP. This coupling structure in the subtropical WNP provids favorable dynamic and water vapor conditions for the occurrence of the subtropical WNP precipitation. This process gives a physical explanation for the relationship between the TP mid upper tropospheric temperature and the subtropical WNP precipitation.