平顶山短时强降水特征及地形增幅作用分析

Analysis of Short-Term Heavy Precipitation Characteristics and Terrain Enhancement Effect in Pingdingshan

摘要: 利用地面逐小时观测资料、ERA5再分析资料、平顶山雷达资料等，分析平顶山短时强降水特征，采用水汽收支方法对一次短时强降水典型天气过程的地形增幅作用机制进行研究，定量化地形降水增幅量。结果表明：1) 平顶山短时强降水频次和最大小时降水量均呈“南多北少、西多东少”的分布特征，与地形密切相关，鲁山山区短时强降水发生频次比周围要多5~10次，80 mm/h以上的站点多出现在鲁山境内的伏牛山山脉迎风坡的喇叭口区域；2) 短时强降水站次最多的年份为2021年，小时降水量在20~30 mm之间的站次占比均超过50%以上，短时强降水发生时间的日变化呈明显的双峰特征，峰值出现在午后(14~16时)和凌晨(00~02时)；3) 2021年8月22日天气过程受副热带高压减弱南退配合低槽东移共同影响并叠加中尺度配合倒槽顶部的辐合作用，为大暴雨天气提供了充足的动力条件；4) 低层的偏东气流在地形阻滞抬升作用下，触发对流生成，雷达图上表现为强回波带稳定少动，形成准静止型回波，造成鲁山南部局地出现大暴雨；5) 伏牛山迎风坡地形降水增幅量可达20 mm以上，是实况累积量的30%，局地超过60%。

Abstract: By utilizing ground hourly observation data, ERA5 reanalysis data, and Pingdingshan radar data, this study analyzes the characteristics of short-time heavy rainfall in Pingdingshan. The water vapor budget method is employed to investigate the terrain enhancement mechanism of a typical short-time heavy rainfall event, achieving a quantitative assessment of terrain-induced precipitation enhancement. The results show that: 1) The frequency and maximum hourly precipitation of short-term heavy precipitation in Pingdingshan both exhibit a spatial distribution pattern of “more in the south and less in the north, more in the west and less in the east”. And it’s closely related to topography. The frequency in the Lushan mountainous area is 5~10 times higher than in surrounding regions, and stations recording hourly precipitation exceeding 80 mm/h are mostly located in the “trumpet-shaped” windward slope area of the Funiu Mountains; 2) The highest number of stations experiencing short-term heavy precipitation was in 2021. Station occurrences with hourly precipitation between 20~30 mm accounted for over 50% of all years. The daily variation of short-term heavy precipitation shows a distinct bimodal pattern, with peaks occurring in the afternoon (14:00~16:00) and early morning (00:00~02:00); 3) The weather process on August 22, 2021 was affected by the weakening and southward retreat of the subtropical high and the eastward movement of the low trough, and superimposed with the convergence of the mesoscale and the top of the inverted trough, which provided sufficient dynamic conditions for the heavy rainstorm weather; 4) Low-level easterly flows, obstructed and lifted by terrain, triggered convective development. Radar showed a persistent and quasi-stationary strong echo band, leading to localized heavy rainfall in southern Lushan; 5) The terrain precipitation increment on the windward slope of the Funiu Mountains can exceed 20 mm, accounting for 30% of the observed accumulated precipitation, and locally exceeding 60%.