重庆市区域性暴雨危险性定量分析及其时空分布规律研究

Temporal-Spatial Distribution and Quantitative Risk Assessment of Rainstorms in Chongqing

区域性暴雨是重庆市危害性最大的自然灾害之一,对其研究有助于科学地开展防灾减灾工作。利用重庆市34个国家基本气象站逐日降水资料,采用概率统计、Matlab小波分析和ArcGIS空间分析等方法,研究1962～2016年重庆市发生的176场区域性暴雨危险度及其时空分布规律。得出如下结论：选择区域性暴雨平均降水量、日降雨极值、区域性暴雨覆盖范围和持续时间4个指标评价重庆市区域性暴雨危险度。在176场区域性暴雨中,轻度危险出现83次,占47.16%;中度危险49次,占27.84%;重度危险35次,占19.89%;极重度危险9次,占5.11%。从时间变化上看,6月和7月是重庆市区域性暴雨的多发期,7月区域性暴雨危险度平均指数最高,其他月份相对较低;重庆市年区域性暴雨危险度存在7a和28a的变化周期;各年代的区域性暴雨发生次数及其危险度差异较小,但各年代内区域性暴雨危险度等级构成差异较大。从空间分布上看,区域性暴雨中心地区差异明显,渝东北部地区的开州和渝西部地区的荣昌是重庆市区域性暴雨中心;各季节的区域性暴雨中心也存在明显差异,春季区域性暴雨中心主要出现在渝西部地区,夏季主要出现在渝东北部和渝西部地区,秋季主要出现在渝东北部地区。

The regional rainstorm is of the worst natural disasters in Chongqing,and a systematical study on it is much needed for disaster prevention and mitigation. The risks and spatial-temporal distributions of regional rainstorm in Chongqing were systematically studied by using probability statistics,Matlab wavelet analysis and ArcGIS spatial analysis methods on daily precipitation data documented from 1962 to 2016 at 34 national basic weather stations in Chongqing. The assessing results based on the 4 indexes of average rainfall volume,24 h-rainfall extreme value,coverage and duration of the regional rainstorm indicated that,among the recorded 176 regional rainstorms,mild risk rainstorms accounted for 47. 16%（ 83 times）,moderate risk rainstorms accounted for 27. 84%（ 49 times）,severe risk rainstorms accounted for 19. 89%（ 35 times） and extremely severe risk rainstorms accounted for 5. 11%（ 9 times）.In terms of the temporal distribution,the regional heavy rainstorms occur frequently in June and July and relatively less in other months,the highest average regional rainstorm risk index occurs in July; two variation periods of 7-years and 28-years could be identified,and the number and severity of regional rainstorm in different periods were quite similar but the grade composition of regional rainstorm were different significantly. In terms of the spatial distribution,the occurrence of regional rainstorms in center Chongqing were different from around areas,Kaizhou（ northeastern Chongqing） and Rongchang（ western Chongqing） were centers of regional rainstorm; furthermore,the regional rainstorm center changed in different seasons,it often occurred in the western Chongqing in spring,in the northeastern and western Chongqing in summer,and in the northeastern Chongqing in autumn.