青藏高原和热带印度洋5月热力异常与新疆夏季降水的关系

基于1979-2017年美国国家海洋和大气管理局(NOAA)提供的海表温度资料和美国国家环境预测中心(NCEP)/美国国家大气研究中心(NCAR)提供的大气环流再分析资料以及青藏高原地区149个站点观测资料计算的地表感热通量和新疆气象信息中心提供的全疆81站逐月降水资料等,研究了5月青藏高原和热带印度洋加热对新疆夏季降水的单独影响和共同影响。结果表明:5月高原感热和印度洋海表温度的异常呈较好的持续性,异常可持续至夏季。奇异值分解(SVD)分析发现5月高原东部(90°E为界)感热与新疆北部及塔里木盆地西南部夏季降水呈显著负相关,热带印度洋海温与塔里木盆地西部夏季降水呈显著正相关。当仅考虑高原感热影响时,高原东部感热偏强(弱)时,对应北疆夏季降水将偏少(多);当仅考虑热带印度洋海温影响时,海温偏暖(冷)时,塔里木盆地西部地区夏季降水偏多(少)。当高原感热和热带印度洋海温均偏强(弱)时,北疆夏季降水将偏少(多),南疆夏季降水将偏多(少)。当高原感热偏强(弱),热带印度洋海温偏弱(强)时,中亚副热带西风急流位置偏北(偏南),中亚和贝加尔湖地区上空分别为异常反气旋(异常气旋)和异常气旋(异常反气旋)控制,新疆上空盛行偏北(南)风,同时热带印度洋水汽不能(能)输送至新疆上空导致新疆夏季降水偏少(多)。

Relationships between Thermal Anomalies over the Qinghai-Xizang Plateau and Tropical Indian Ocean in May with Summer Rainfall in Xinjiang

Based on the sea surface temperatures(SSTs)data provided by the National Oceanic and Atmospheric Administration(NOAA),reanalysis data provided by the National Center for Environmental Prediction(NCEP)/National Center for Atmospheric Research(NCAR),the surface sensible heat flux calculated at 149 stations in May over the Qinghai-Xizang Plateau(QXP)from 1979 to 2017,and the monthly precipitation data at 81 stations in Xinjiang provided by the Xinjiang Meteorological Information Center,the concurrent and individual effects of thermal anomalies over the tropical Indian Ocean(IO)and the QXP in May on summer rainfall in Xinjiang are analyzed. The results show the thermal anomalies in in May have good heating persistence with summer sensible heat(SH)and summer SSTs over the QXP and tropical IO. The singular value decomposition(SVD)analysis indicates the SH over the eastern QXP(divided by 90 E)in May has a good negative correlation with summer rainfall in northern Xinjiang and southwest Tarim Basin(TB),and the SSTs over the tropical IO have a good positive correlation with summer rainfall in western TB. When only considering the heating effects over the QXP,the strengthened(weakened)SH over eastern QXP is corresponded to less(more)summer rainfall in the northern Xinjiang and southwest parts of the TB. When only considering the heating effects over the tropical IO,the warmer(colder)SSTs are corresponded to more(less)summer rainfall over the TB. When corresponding to stronger SH in the QXP and warmer SSTs over the tropical IO in May,the northern Xinjiang(TB)receives less(more)summer rainfall. When corresponding to weaker SH in the QXP and colder SSTs over the tropical IO in May,less summer rainfall occurs over the western TB and northeast Xinjiang and the remaining regions receive more summer rainfall. When the SH is weaker(stronger)over the QXP and the SSTs are warmer(colder)over the tropical IO,the subtropical westerly jet shifts south(north)over central Asia,anomalous south(north)wind prevails over Xinjiang and more(less)water vapor is transported into Xinjiang from the IO.Above all are contributed to more(less)summer rainfall over Xinjiang.