ON THE RELATIONSHIP BETWEEN PRECIPITATION ANOMALIES IN THE FIRST RAINING SEASON (APRIL-JUNE) IN SOUTHERN CHINA AND SST OVER OFFSHORE WATERS IN CHINA

Precipitation anomalies in the first raining season of southern China were analyzed,with the suggestion that there are obvious interannual variation of peak values.In the raining season,the general tendency of precipitation is not obvious and the anomalous oscillation is multi-scale.Corresponding to years of more or less precipitation in the raining season,there are sharply opposite distribution across the nation in the simultaneous periods.In addition,by studying the distribution of correlation between anomalous precipitation in southern China in the first raining season and SSTA over offshore waters of China in the preceding period (June ～August of the previous year),a sensitive zone of waters has been found that has steady effect on the precipitation of southern China in the season.Discussions are also made of the sensitive period,its simultaneous SSTA and subsequent anomalous circulation field in relation to precipitation anomalies and simultaneous circulation field in the first raining season of southern China.In the last part of the work,relationship between the SSTA in the sensitive zone and global SSTA is analyzed.A possible mechanism by which SSTA in offshore Chinese waters affects the precipitation anomalies in the first raining season of southern China is put forward.

广东前汛期锋面强降水和后汛期季风强降水特征对比分析

应用近二十年的历史观测资料和EC再分析资料,对由锋面和季风槽两种不同天气系统影响下广东发生的两组暴雨过程的天气形势、降水/短时强降水落区及其对流活动和物理量特征进行了诊断分析和对比分析。结果表明:无论是前汛期锋面降水还是后汛期季风降水,珠三角(珠江三角洲)地区都是次中心,有大到暴雨量级降水。珠三角地区也是小时雨量≥50 mm的短时强降水高发区。前汛期锋面对流活动的抬升凝结高度约在900～850 hPa,南北方向的温度梯度提供了斜压不稳定能量,0～3 km强的风垂直切变使对流易于维持和发展;对流区有较强的水汽通量辐合;风暴相对螺旋度较大,对流的旋转性和沿着旋转方向的移动特征明显。相对而言,后汛期季风强降水对流凝结高度更低,对流活动具有正压的热带对流性质,可在弱的水汽通量辐合和垂直风切变环境中维持,但对流强度不如前汛期。以上结论可为同类天气的短期和短临主客观预报提供预报思路和依据。