梅州汛期暴雨频次异常与大气环流的关系

Relationship between Anomalous Frequencies of Torrential Rain during the Flood Season of Meizhou and the Atmospheric Circulation

采用1961—2014年梅县气象站降水及NCEP再分析资料,应用统计学方法,探析梅州汛期暴雨频次异常与大气环流关系。结果表明:近54年来梅州汛期可分为2个多暴雨期和2个少暴雨期,2007年出现了汛期暴雨频次的突变。前汛期暴雨异常偏多年,200 h Pa南亚高压异常偏弱,500h Pa高纬地区高压脊偏强,南支槽活跃;850 h Pa西南风偏强,水汽充沛;南海及菲律宾以东洋面海温偏高,黑潮区海温偏低。后汛期暴雨异常偏多年,200 h Pa南亚高压偏强;500 h Pa华南处在偏强副高的南侧;850 h Pa南海上空为两股异常气流的切变区域,有利于南海季风槽的发展和维持;海温场与La Ni1a年的海温分布型相似,有利于影响梅州的热带气旋偏多。而前后汛期暴雨异常偏少年的各层形势均不利于强降水的发生。

Using precipitation data of a meteorological station at Meixian and NCEP reanalysis from 1961 to 2014 and with the methods of statistics, we study the relationship between anomalous frequencies of torrential rain during the flood season of Meizhou and the atmospheric circulation. The result is shown as follows. Over the 54 years, the flooding season can be divided into two periods of anomalously more rain （MR） and two periods of anomalously less rain （LR） , and an abrupt change occurred in 2007 in the frequency of torrential rain. In the years of MR, a 200 hPa high was anomalously weaker in South Asia while a 500 hPa high ridge was anomalously stronger in high latitudes. The southern branch of the westerlies was active, a southwest monsoon was strong at 850 hPa, providing sufficient amount of water vapor. Sea surface temperature （SST） was relatively high in the South China Sea and waters to the east of the Philippines but relatively low in Kuroshio. In the years of MR during the annually second flood season, the South Asia high （ at 200 hPa） was relatively strong, the south of China （at 500 hPa） was at the south side of a relatively strong subtropical high and there was a zone of shear by two anomalous airflows over the South China Sea （at 850 hPa） , conducive to the development and maintenance of a monsoonal trough over the sea. The SST field was similar to that of a La Nina year, which increased the number of tropical cyclones that affected Meizhou. By contrast, in the years of LR in both the annually first and second flooding seasons, the patterns of all individual levels are such that they are not conducive to the occurrence of intense precipitation.