四川山地暖季夜间暴雨的空间分布以及对海拔高度的依赖性

四川盆地是我国夜雨发生频次最高的地区，夜间暴雨是夜雨中可致灾并加剧防范难度的一类特殊气象灾害，但以往对四川山地夜间暴雨精细特性的相关研究较少。利用四川省2010—2019年2 165个国家及区域气象站逐小时降水资料，分区统计了四川暖季（5—9月）暴雨日夜间降水占日降水量的比例、夜间暴雨频次和夜间平均暴雨强度的基本特征，并通过趋势分析和地理加权回归等统计方法，分析了其空间分布及其与海拔高度的关系，获得以下结果：（1）四川暴雨日夜间降水占日降水量比例呈现自南向北递减的趋势，以海拔2 800 m为分界，表现为随海拔高度升高呈先增大、后减小的垂直分布特征，川西南山地与其他山地区域整体上升的变化趋势明显不同。（2）夜间暴雨频次较多的测站沿川西与川西南山地陡峭地形呈线性分布，夜间暴雨频次随海拔高度升高总体呈现减小的特征，川西山地和川西南山地的频次最大值分别出现在海拔800 m和500 m。（3）四川夜间平均暴雨强度整体随海拔的升高而减小，大值区主要位于川西山地和川东北山地，海拔700 m高度处的峰值强度主要由川西山地贡献。（4）川西山地夜间暴雨特征呈次数较多且每次强度大，川西南山地夜间暴雨为次数多但单次降水量较小，而川东北夜间暴雨的强度较大但次数较少。以上结果有助于深化对山地夜间暴雨精细特征的认识。

Spatial Distribution of Nighttime Rainstorms in Warm Season in Sichuan Mountains and the Dependence on Altitude

Sichuan Basin is the region with the highest frequency of night rain in China. Nighttime rainstorm is a special meteorological disaster that can cause disasters and increase the difficulty of prevention. However, there are few related studies on the fine features of night rainstorm in Sichuan mountains in the past. Using the hourly precipitation data of 2 165 national and regional meteorological stations in Sichuan Province from 2010 to 2019, the basic characteristics of the ratio of nighttime precipitation to daily precipitation on rainstorm days, nighttime rainstorm frequency and average nighttime rainstorm intensity in the warm season (from May to September) in Sichuan were calculated by region. Through statistical methods such as trend analysis and geographically weighted regression, its spatial distribution and its relationship with altitude were analyzed. The following results were obtained: (1)The ratio of nighttime precipitation to daily precipitation on rainstorm days in Sichuan showed a decreasing trend from south to north, with an altitude of 2 800 m as the boundary, showing a vertical distribution characteristic of increasing first and then decreasing with the increase of altitude. The trend of southwestern Sichuan mountains was obviously different from the overall rising trend of other mountains. (2)Stations with more frequent rainstorms at night were linearly distributed along the steep terrain of western and southwestern Sichuan mountains. The frequency of nighttime rainstorm generally decreased with the increase of altitude. The maximum frequency of the western and southwestern Sichuan mountains respectively occurred at 800 m and 500 m above sea level. (3)Average nighttime rainstorm intensity in Sichuan decreased with the increase of altitude, and the high-intensity area was mainly located in the western and northeastern mountains of Sichuan. The peak intensity at the altitude of 700 m was mainly contributed by western Sichuan mountains. (4)The nighttime rainstorms in western Sichuan mountains were characterized by more frequent and strong intensity each time. There were many heavy rainstorms at night in southwestern Sichuan mountains, but the single precipitation was small. The nighttime rainstorms in Northeast Sichuan mountains were strong but less frequent. The above results help to deepen the understanding of the fine characteristics of mountain nighttime rainstorms.