南亚高压的多模态特征及其与新疆夏季降水的联系

Characteristics of Different Patterns of South Asia High and Their Relationships with Summer Precipitation in Xinjiang

基于欧洲中期天气预报中心(ECMWF)的Interim再分析资料(ERA-Interim)和新疆88个观测站点降水资料,分析了1979—2013年夏季(7月和8月)南亚高压多模态特征及其与新疆夏季降水的关系。结果表明,南亚高压除了青藏高压型和伊朗高压型外,还存在双体型。伊朗高压型和双体型分布产生的降水占新疆夏季总降水的70%~90%,青藏高压型分布产生的降水相对较少,占10%~30%。南亚高压的多模态分布对新疆降水有不同影响,伊朗高压型时,北疆部分地区和东疆降水偏多,塔里木盆地降水偏少;青藏高压型时,除塔里木盆地西南部降水偏多外,新疆其余地方降水均偏少。南亚高压双体型对塔里木盆地夏季降水影响最为突出,当夏季南亚高压呈双体型分布时,塔里木盆地降水偏多。合成分析发现,南亚高压双体型中心位置变化对环流和水汽输送产生不同影响,因而对应的塔里木盆地夏季降水也存在一定差异。当两个中心位置同时偏西时,塔里木盆地中西部地区降水偏多,水汽分两步进入塔里木盆地。当两个中心位置同时偏北时,整个塔里木盆地降水增加,水汽沿着青藏高原东侧绕流进入塔里木盆地。

By using the ERA-Interim reanalysis data and precipitation data which was provided by 88 observation stations in Xinjiang,the relationships between the characteristics of different patterns of South Asia High and the summer precipitation（ July and August） in Xinjiang during 1979—2013 were analyzed. The results showed that except Iran high pattern and Qinghai-Tibetan high pattern,the South Asia High could also be divided into Two centers pattern and Multiple centers pattern. The precipitation of Iran high pattern and Two centers pattern accounted for 70% ~ 90% of summer total precipitation in Xinjiang,while the precipitation of Qinghai-Tibetan high pattern accounted for 10% ~ 30% of summer total precipitation. Iran high pattern,Qinghai-Tibetan high pattern and Two centers pattern have different characteristics,and different patterns of South Asia High have different effects on the summer precipitation in Xinjiang. The precipitation of Iran high pattern increased in most parts of northern and eastern Xinjiang and decreased in the Tarim Basin in Xinjang compared to the averaged summer precipitation. Qinghai-Tibetan high pattern had the opposite precipitation distribution compared with the precipitation distribution of Iran high pattern. The precipitation of Qinghai-Tibetan high pattern decreased in most parts of Xinjiang except in southwestern parts of the Tarim Basin compared to the averaged summer precipitation. Two centers pattern had the largest impact on summer precipitation in the Tarim Basin. The precipitation of two centers pattern increased in the Tarim Basin compared to the averaged summer precipitation while the precipitation of Iran high pattern and QinghaiTibetan high pattern decreased in Tarim Basin. Based on the method of composite analysis,the results indicated that the changes of two centers positions of South Asia High had different impacts on circulation and moisture transport. Due to the different characteristics of circulation and moisture transport,the distributions of summer precipitation in the Tarim Basin were relatively different. The precipitation in central and western parts of the Tarim Basin increased compared to the averaged summer precipitation when two centers of South Asia High were both on the west of the averaged longitude,and the water vapor came into the Tarim Basin in Xinjiang from lowlatitudes by a two-step process. The precipitation in the whole Tarim Basin increased compared to the averaged summer precipitation when two centers of South Asia High were both on the north of the averaged latitude,and the water vapor came into the Tarim Basin along the east side of Qinghai-Tibetan Plateau.