华南前汛期持续暴雨环流分型初步研究

采用1961—2010年NCEP/NCAR逐日再分析资料和台站观测降水量资料,按一定标准选取了华南前汛期24个持续暴雨过程;并且按基本判据确定逐年华南夏季风降水开始日期。然后依据南亚高压环流型和相对于该年夏季风降水开始的早晚,将这些暴雨过程划分为夏季风降水前、后南亚高压东部型,夏季风降水后南亚高压带状、西部型共4个类型;其中,夏季风后南亚高压西部型次数最多、平均持续时间最长。所有类型持续暴雨的相同点是:广东东北部附近均为暴雨频率和雨量高值区;暴雨期间华南150 h Pa位势高度增加、500 h Pa位势高度减少;华南处在150 h Pa偏西风急流南侧辐散区中;850 h Pa华南沿海有明显的西南气流,低层辐合在华南东北部最明显;两广沿海为可降水量大值区;华南的整层水汽输送主要呈现西南向。不同点是:夏季风后南亚高压西部型平均雨量较小,夏季风后南亚高压带状型与西部型在印度洋上存在明显的偏东风高空急流;夏季风后南亚高压类型在两广沿海的可降水量数值较大。

Preliminary research on circulation patterns in the persistent heavy rain processes during the first rainy season in South China

Based on the NCEP/NCAR daily reanalysis data and observational rainfall data from 1961 to 2010,24 persistent heavy rain events are selected in the first rainy season in South China,and the beginning dates of annual South China summer monsoon rainfall(SCSMR) are chosen according to the basic criterion.According to the SCSMR beginning date and the average circulation pattern of South Asia High(SAH) at 150 hPa during a heavy rain event,the 24 persistent heavy rain events fall into four categories,including east SAH pattern before SCSMR,east SAH pattern after SCSMR,belt SAH pattern after SCSMR,and west SAH pattern after SCSMR.Among them,west SAH pattern after SCSMR is the most with the longest average duration.The same points of persistent heavy rain events in all SAH patterns show that:The center of both high frequency and large rainfall locates near northeast Guangdong Province;During the heavy rain,South China geopotential height increases at 150 hPa but decreases at 500 hPa;South China lies in the 150 hPa divergence zone to south side of westerly jet;The southwesterly is obvious over coastal area of South China at 850 hPa,and the low level convergence over northeast South China is the most obvious;Precipitable water vapor(PWV) over coastal area of both Guangdong and Guangxi provinces is the most.Direction of water vapor transportation integrated from surface to 300 hPa is mainly southwest over South China.The differences show that the mean rainfall is the least in the west SAH pattern after SCSMR;The easterly jet over the Indian Ocean emerges in both the belt and the west SAH patterns after SCSMR;PWV in the patterns after SCSMR is larger than that in the pattern before SCSMR over the coastal area of both Guangdong and Guangxi provinces.