中南半岛和华南地区极端降水时空特征

Spatiotemporal Characteristics of Extreme Precipitation in the Indochina Peninsula and South China

全球变暖使得极端降水事件的强度和频率均呈上升趋势,位于亚洲季风区的中南半岛和华南地区更易受到极端降水影响而发生洪涝灾害。本文利用逐日降水资料对1951~2015年中南半岛和华南地区湿季(5~10月)的极端降水事件进行客观分类,并对每一类极端降水事件的大尺度流型特征及年际、年代际和长期趋势特征进行了分析。结果表明:(1)根据降水中心位置,中南半岛和华南地区的极端降水可客观分为华南类、中南半岛类、缅甸—云南类和华南南部—越南北部类,它们所联系的大尺度流型以中高纬波列和热带偶极子环流为主。其中,华南类的大尺度流型在对流层高层为类似于东亚—太平洋(East Asia–Pacific,简称EAP)遥相关型的“+−+”经向型波列,但中心位置较典型EAP型偏西南,中东部的负异常环流为关键系统,低层为位于低纬度地区的“+−”经向型波列。中南半岛类大尺度流型为热带偶极子异常环流,对流层低层较高层更为显著宽广。其余两类极端降水大尺度流型特征为在对流层高层受Rossby波列影响,低层主要为偏弱的热带偶极子异常环流。(2)中南半岛和华南地区极端降水的频次呈显著上升的趋势,主要来自于华南类和中南半岛类极端降水的贡献。其中,“+−+”经向型波列的频发是造成华南类极端降水增多的原因。(3)中南半岛与华南地区极端降水的空间分布具有反对称特征。

Extreme precipitation events have become more intense and frequent as a result of global warming.The Indochina Peninsula and South China(INCSC)are located in the monsoon region and thus are vulnerable to heavy rainfall and flooding.This study examined the INCSC regions’extreme precipitation events during the wet season(May–October)from 1951 to 2015.The circulation features,interannual,interdecadal,and long-term trend characteristics of each extreme precipitation cluster were examined.The findings reveal that(1)the extreme precipitation in the INCSC region are objectively grouped into South China,Indochina Peninsula,Burma–Yunnan,and southern South China–Northern Vietnam clusters based on the position of the precipitation center.Their associated large-scale meteorological patterns(LMP)are primarily characterized by mid-high latitude wave trains and the tropical dipole circulation.The South China clusters’LMP has a“+−+”meridional wavetrain in the upper troposphere,which resembles the East Asia–Pacific(EAP)teleconnection pattern.However,the LMP centers are located southwestward with respect to their EAP counterparts.The key system is the negative anomaly circulation in central East China.LMP features have a“+−”meridional wavetrain in the lower troposphere,which is located at low latitudes.The Indochina Peninsula clusters’LMP is associated with a dipole anomaly circulation,which is broader in the lower troposphere than the upper troposphere.The LMPs of the two extreme precipitation clusters have a combination of Rossby wavetrain in the upper troposphere and the moderate tropical dipole in the lower troposphere.(2)The occurrence of extreme precipitation events in the INCSC region exhibits a significant upward trend,which is contributed by the South China and Indochina Peninsula clusters.The meridional wavetrain LMP occurrence frequency enhanced the extreme precipitation events in the South China cluster.(3)The spatial distribution of extreme precipitation of the Indochina Peninsula and South China clusters are antisymmetric with each other.