由河南

气象风险预警指标的确定是山洪灾害气象风险预报预警业务中的关键技术问题。采用前期影响雨量表征流域前期土壤含水量饱和度，并用四分位数法划分为4个等级；采用P-Ⅲ型频率分析法求得4个重现期(＜5、≥5、≥20、≥50 a)的洪峰流量以及山洪发生前5个时间尺度(1、3、6、12、24 h)降雨量；以洪峰流量的4个重现期分别表征山洪灾害气象风险预警4个等级(Ⅳ、Ⅲ、Ⅱ、Ⅰ级)，基于信息扩散技术建立气象风险等级与流域前期土壤含水量饱和度、不同时间尺度降雨量的信息矩阵，即气象风险预警组合指标。利用淠河流域历史降水与流量极值资料，以及2003—2012年17次典型洪水过程气象水文资料，建立5个时间尺度的山洪灾害气象风险4个等级预警组合指标，并利用40组独立洪水样本，对不同时间尺度气象风险预警组合指标进行应用检验，总体预警合格率达到70%，表明该方法应用于山洪灾害气象风险预警是可行的。

Analytical results for operational flash flood guidance

Identification of the early warning indicators of meteorological risks is a key technical issue in the forecast of flash flood disasters. The antecedent precipitation is used to characterize the degree of antecedent soil moisture saturation of a river basin, which is divided into four levels based on the quartile method. Frequency analysis based on the Pearson Ⅲ distribution (P-Ⅲ) model yields the estimates of the peak flow of four return periods (< 5, ≥5, ≥20, and ≥50 a) and rainfall of five durations (1-, 3-, 6-, 12-, and 24 h) before the occurrence of flash flood. The four return periods of peak flow are used to characterize the four meteorological risk levels (Ⅳ-, Ⅲ-, Ⅱ-, and ⅠLevel) of flash flood disasters. The information diffusion technique is used to establish the matrices of meteorological risk levels, antecedent soil moisture saturation degrees, and rainfall of different durations to form a combined indicator for the warning meteorological risks. Based on historical records of rainfall and extreme flow in the Pihe basin, 17 flash flood events between 2003 and 2012 are analyzed with the proposed method to derive the four-level meteorological risk warning indicators for flash flood at five time steps. The tests of the derived risk warning indicators in 40 independent historical flash flood events at different time steps have yielded a correct warning rate of over 70%, which demonstrates the feasibility of using the method for flash flood disaster warnings.