近50a江淮梅雨期暴雨的区域特征

Regional Features of the Torrential-Rain of the Meiyu Period in the Changjiang-Huaihe Region

利用江淮地区44个站1954—2003年近50 a逐日降水资料,采用模糊聚类和经验正交函数分解(EOF)方法分析了江淮梅雨期暴雨的时空变化特征。结果表明:梅雨期暴雨量存在显著的区域差异,可以分为南、北两个区;梅雨期暴雨量具有显著的候际、月际、年际和年代际变化特征,南区暴雨量峰值出现在6月第5候,北区峰值出现在6月第5候和7月第1候;南区暴雨贡献率大于北区,而北区暴雨集中率大于南区;南区暴雨量长期变化呈显著的上升趋势,而北区变化不明显;南北两区暴雨量均存在不同时间尺度的振荡周期。

On the basis of the daily precipitation of the Meiyu period at 44 stations in the Changjiang-Huaihe region from 1954 to 2003, the temporal evolution and spatial distribution characters of torrential-rain （ ≥ 50 mm/d ） are investigated in terms of fuzzy cluster method and empirical orthogonal function （ EOF ） decomposition. Results show that the Changiiang-Huaihe region is divided into south and north area according to the prominent reginal difference of torrential-rain rainfall;there are prominent inter-pentadly, inter-monthly, inter-annual, inter-decadal variabilities in the torrential-rain rainfall of the Meiyu period; the peak value of torrential-rain rainfall appears in the fifth pentad of June in south area and in the first pentad of July and the fifth pentad of June in north area; the contribution rate of torrential-rain to the total rainfall of the Meiyu period in south area is higher than that in north area, while the concentration rate （ the ratio of Meiyu torrential-rain rainfall to annual torrential-rain rainfall ） in north area is higher than that in south area;the torrential-rain rainfall shows a remarkable long-term ascending trend in south area, but no evident trend in north area; there are different time scale oscillations in the torrential-rain in both south and north area.