金沙江下游白鹤滩水电站"6·28"极端强降雨特征研究

本文利用1960～2019年日降水量资料分析了白鹤滩水电站极端降水变化特征，指出宁南和巧家两县极端降水量、极端降水日数和极端降水比率均呈上升趋势。宁南极端降水阈值为42.9mm，宁南、巧家平均每年极端降水日数相近，为2～3天。极端降水发生的高峰期在6月、其次7月。利用ERA5再分析资料，对“6.28”典型白鹤滩暴雨过程进行物理量诊断分析，得出此次强对流暴雨天气过程发生期间，白鹤滩水电站对流层低层水汽通量辐合较强，水汽的积聚对暴雨的维持提供条件。垂直速度场表现为较强的垂直上升运动，同时对流层低层假相当位温随高度降低，反映了大气的不稳定性，为局地产生强对流性降水天气提供了有利条件。由此次白鹤滩突发暴雨灾害，对气象服务启示要从单纯重视“过程前”的预报服务模式向关注“过程中”的跟踪式预报服务模式转变。 

Study on the Characteristics of “6·28” Extremely Heavy Rainfall of Baihetan Hydropower Station on the Lower Jinsha River

This paper analyzes the characteristics of extreme precipitation changes in Baihetan Hydropower Station using the daily precipitation data from 1960 to 2019,and points out that extreme precipitation,extreme precipitation days and extreme precipitation ratios in Ningnan and Qiaojia counties are on the rise. The extreme precipitation threshold in Ningnan is 42.9 mm,and the average annual extreme precipitation days in Ningnan and Qiaojia are similar,2-3 days. Extreme rainfall peaked in June and the next in July. Using ERA5 reanalysis data,the physical quantity diagnosis and analysis of the typical "6.28" Hehetan rainstorm process is carried out,and it is concluded that during the occurrence of this strong convective rainstorm weather process,the flux of Baihetan Hydropower Station has strong convection of low-level water vapor,and the accumulation of water vapor provides conditions for the maintenance of heavy rain. The vertical velocity field shows strong vertical upward motion,while the hypothermia of the troposphere decreases with altitude,reflecting the instability of the atmosphere and providing favorable conditions for the local generation of strong convective precipitation weather. From the sudden heavy rain disaster in Baihetan,the enlightenment to meteorological services should change from a forecasting service model that pays sole attention to "process" to a tracking service model that pays attention to the process.