8月中国低纬高原水汽输送过程及其与降水量极端异常的联系

利用1979—2010年ERA-Interim再分析资料、全球降水气候中心(Global Precipitation Climate Center,GPCC)的降水量资料和站点降水观测资料,通过引入水汽贡献率和水汽通过率,构建描述降水量对水汽源地蒸发量的敏感性指数等方法,揭示了8月流入低纬高原水汽的输送过程的气候特征,及其与8月低纬高原降水量极端异常的联系。结果表明:(1)8月流入低纬高原水汽的重要源地是中南半岛北部和华南一带的陆地区域,以及北部湾和孟加拉湾北部西南至东北的狭长海面。(2)8月流入低纬高原水汽的主要输送通道有两条:孟加拉湾上空狭长的西南季风;经17°N附近偏东季风在南海西北部110°E附近发生转向后的东南季风。那加丘陵和中南半岛北部的纵向岭谷明显阻挡了两支水汽输送通道。(3)8月流入低纬高原水汽主要受大气环流影响,受水汽源地蒸发量的直接影响有限。当流入低纬高原水汽异常偏多(少)时,使得可降水量偏多(少),最终导致降水量偏多(少)。

The moisture transportation process in low latitude plateau of China and its relation with precipitation extreme anomalies in August

By using the ERA-Interim reanalysis data, precipitation data provided by the Global Precipitation Climate Center (GPCC) and the precipitation at weather stations from 1979-2010, the sensitivity index describing the precipitation to the evaporation of water vapor source was constructed, which reveals the climatic characteristics of the water vapor transport process into the low latitude plateau in August and its relationship with the extreme anomaly of precipitation on the low latitude plateau in August. Results show that (1) the important sources of water vapor flowing into the low latitude plateau in August are the land areas in the north of Indochina Peninsula and South China, as well as the narrow sea surface from southwest to northeast in the Beibu Gulf and the north of the Bay of Bengal. (2) There are two main transport channels of water vapor flowing into the low latitude plateau in August:the narrow southwest monsoon over the Bay of Bengal; after the easterly monsoon near 17°N, it turns to the southeast monsoon near 110°E in the northwest of the South China Sea. The Naga Hills and the longitudinal mountains and valleys in the north of Indochina Peninsula obviously block the two water vapor transmission channels. (3) The water vapor flowing into the low latitude plateau in August is mainly affected by the atmospheric circulation and is limited by the evaporation of the water vapor source. When the abnormal water vapor flowing into the low latitude plateau is too much (less), the precipitable amount is too much (less), and finally the precipitation is too much (less).