1963—2012年连平县暴雨的气候变化特征

On the Characteristics of Climatological Variation of Torrential Rain from 1963 to 2012 in Lianping County

利用1963—2012年连平县逐日降水资料,采用统计方法分析了近50年来连平县暴雨的逐月分布及年际与年代际变化特征,并对暴雨的初终日变化及持续天数等也进行了分析。结果表明:连平每个月都有暴雨出现的可能,但主要集中在4—9月,暴雨与大暴雨日数均具有单峰特征,峰值都出现在6月。暴雨日的年际变化大,近50年来,连平县年暴雨中日数呈减少趋势,且与年降水量存在着显著正相关。取NCEP再分析资料的月平均850、200 h Pa经纬风u、v资料,分析了暴雨偏多年和偏少年的大气环流背景,结果表明:6月连平高空的高、低层环流对形成暴雨最为有利。而暴雨偏少年,前汛期各月连平高空通常没有明显的高层辐散及低层辐合异常,不利于上升运动及水汽输送的加强,这是导致这些年份持续性暴雨偏少的一个主要原因。

With the day-to-day precipitation data of Lianping County from 1963 to 2012, this paper sta- tistically studies the characteristics of interannual and interdecadal variations as well as the monthly distribu- tion of torrential rain （TR） in the county over the past 50 years, and analyzes the variation of the annually first and last day of TR and the number of persistent TR days. The results are shown as follows. It is possible for Lianping to have TR every month of the year but April through September is the time when it mostly oc- curs. The numbers of both TR days and unusual TR days are unimodal with peaks all appearing in June. The number of TR days varies much on the interanuual scale. Over the past 50 years, the number of TR days tends to decrease in the county and is much positively correlated with the annual rainfall. With the monthly mean NCEP reanalysis data of u and v wind at 850 and 200 hPa, this paper studies the background of atmospheric circulation in the years of more and less TR and the result is shown as follows. The circulation at the upper and low levels in June is the most favorable pattern for TR. In the years of less TR, upper-level divergence and anomalous low-level convergence are not well-defined in the annually first raining season, unfavorable for the enhancement of ascending motion and water vapor transport. It is one of the main causes for persistently less TR in the years studied.