青藏高原中东部暖季极端降水的区域特征及其典型环流

Regional Characteristics and Typical Circulation of Extreme Precipitation in the Warm Season over the Central and Eastern Qinghai-Xizang Plateau

基于1982-2020年青藏高原中东部105个气象站点逐日降水资料和NCEP/NCAR再分析资料,分析了暖季极端降水的时空异常特征、主要落区和典型环流。结果表明:(1)1982-2020年,青藏高原中东部暖季降水总量整体呈显著增加趋势(P<0.05),气候倾向率达10.7 mm·(10a)^(-1),但存在明显的区域性差异和年代际变化特征。极端降水指标在1990s和2000s中后期发生了年代际趋势转变,2009年之后极端降水的增加最为突出,气候倾向率可达整体增加水平的4~5倍;在三个时段,高原极端降水存在南北趋势反向变化特征,北部极端降水在1998-2009年增加最为突出,南部经历了显著增加-显著减少-显著增加的趋势变化。(2)1982-2020年,青藏高原中东部暖季小范围极端降水频数呈显著减少趋势(P<0.1),而大范围极端降水频数显著增加(P<0.05);4级范围极端降水主要有:东北部型(A型)、南部型(B型)和东南部型(C型)三种主要的落区。(3)西太平洋副热带高压(以下简称西太副高)的位置和强度差异是导致水汽源地和大范围极端降水落区不同的主要原因;当A型大范围极端降水发生时,西太副高异常偏弱,偏东,水汽主要来自太平洋和西风带的输送;当B型发生时,西太副高异常偏强,西伸南压,水汽主要来自印度洋和孟加拉湾;当C型发生时,西太副高异常偏强,西伸北抬,水汽主要来自西北太平洋、南海和孟加拉湾。

Based on NCEP/NCAR reanalysis data and the daily precipitation data from 105 meteorological stations in the central and eastern Qinghai-Xizang Plateau from 1982 to 2020,we investigate the spatiotemporal anomalous characteristics and major falling areas of warm season extreme precipitation and typical circulation of large-scale extreme precipitation in the central and eastern Qinghai-Xizang Plateau.The results show that:(1)Total precipitation of central and eastern Tibetan Plateau in the warm season shows statistically significant increasing at the rate of 10.7 mm·(10a)^(-1)(P<0.05)during 1982-2020,but there are obvious interdecadal trend shifts in the late 1990s and late 2000s.The increase in extreme precipitation of central and eastern Qinghai-Xizang Plateau is most prominent after 2009,and the climate tendency rate is of 4~5 times greater than that of during 1982-2020.In terms of the distribution of spatial climate tendency rates,the trend of extreme precipitation in the southern Qinghai-Xizang Plateau is opposite to that in the central and northern Qinghai-Xizang Plateau in the three periods.The increase of extreme precipitation in the northern Qinghai-Xizang Plateau is the most prominent during 1998-2009,and the extreme precipitation in the southern Qinghai-Xizang Plateau experiences the interdecadal trend shifts of significant increase,significant decrease and significant increase.(2)The small-scale extreme precipitation in central and eastern Qinghai-Xizang Plateau shows statistically significant decreasing trend(P<0.1),while the large-scale extreme precipitation exhibits statistically significant increasing trend(P<0.05)during 1982-2020.According to the locations of precipitation center,the level 4 large-scale extreme precipitation can be divided into three types,that is,northeast type(A type),southern type(B type)and southeastern type(C type).(3)The difference of location and intensity of the West Pacific Subtropical High is the main factor,which leads to the difference of water vapor sources and the locations of large-scale extreme precipitation falling areas.When the A-type large-scale extreme precipitation occurs,the West Pacific Subtropical High is anomaly weaker and eastward,which leads to the water vapor mainly transported from the Pacific Ocean and the westerlies.When the B-type occurs,the West Pacific Subtropical High is anomaly stronger and extending westward and southward,consequently,the water vapor mainly transported from the Indian Ocean and the Bay of Bengal.When the C-type occurs,the West Pacific Subtropical High is anomaly stronger,extending from the westward and northward,resulting in the water vapor mainly transported from the northwest Pacific Ocean,the South China Sea and the Bay of Bengal.