前汛期惠州市强降水气候突变及其环流特征分析

Analysis of the Interdecadal Change of Heavy Rain during the First Rainy Season in Huizhou and its Circulation Characteristics

惠州市地处气候年际变化显著的东亚季风区,近几十年来前汛期强降水事件频繁,尤其自20世纪90年代以来有很多暴雨灾害发生。为了客观地分析惠州前汛期强降水事件的异常情况,利用1967-2009年惠州市降水资料和NCEP/NCAR再分析资料,研究了前汛期惠州强降水的气候变化及其环流特征。结果表明:前汛期惠州市总降水量和暴雨量大,暴雨日数多;它们的年际变化一致,无明显趋势变化。但自1990年代中期至今,强降水异常有增多且强化的趋势。进一步对比惠州前汛期强降水异常事件突变前后的环流特征,强降水偏多(少)年,突变前后低纬地区均呈现偏南(东北)气流异常,而引起强降水偏多(少)年突变的环流形势差异,主要表现为突变后冷空气作用明显,低层北风分量增强;突变前后物理量的差异则主要表现为,突变后强降水偏多年高、低层散度梯度加大,垂直上升运动偏强,对流性不稳定加大,强降水偏少年上述物理量的变化相反;以上差异特征均导致突变后强降水偏多年更易引发或加剧强降水异常,强降水偏少年更不易于强降水的发生。

The interannual variability of heavy rainfall during the first rainy season in Huizhou and its circulation characteristics are investigated by using the daily precipitation data and NCEP/NCAR reanalysis data from 1967 to 2009.The results show that Huizhou is characterized by large amounts of total precipitation,heavy precipitation amount and rainstorm days.Heavy precipitation and rainstorm days are basically in agreement with the time series of the total precipitation.All of their tendency have little change.However,the anomalous heavy rainfall events tend to increase and intensify from middle 1990s up to the present.Coherent changes in atmospheric circulation are identified in tropical and midlatitude systems.Southerly（northeasterly） anomalies prevail over the low latitude region before and after the climate jump when heavy rainfall events increase（decrease） and intensify（weaken）.However,northerly anomalies and cold air are responsable for the increase and intensification in heavy rainfall after middle 1990s.Moreover,with stronger updraft,convective instability,the heavy rainfall is favorable to form and increase after middle 1990s in Huizhou.The situation of decrease and weakening in heavy rainfall is accompanied by stronger northerly anomalies,weaker updraft and convective instability after middle 1990s.