Neighborhood Ensemble Probability Method Based on Ensemble Agreement Scale and Its Application on Quantitative Probability Forecast of Meiyu Frontal Heavy Rainfall
XU Yuan
MIN Jinzhong
ZHUANG Xiaoran
CHEN Yunhui
ZHANG Lu
TIAN Gaoshan
Abstract：Probability forecast is an objective product derived from ensemble forecasts and contains information of uncertainty,which has important reference value for operational decision-making services.In the traditional neighborhood ensemble probability method(NEP),the neighborhood radius is always a constant and does not conform to the scale spectrum involved in the practical weather events.Therefore,the Neighborhood Ensemble Probability based on Ensemble Agreement Scale(EAS_NEP)was introduced,and comprehensive evaluations were conducted for two Meiyu frontal heavy rainfall events in southern China,in order to verify the applicability of this method in such events and promote its popularization in practical operation.The ensemble forecasts obtained by combining the initial condition,lateral boundary and physical process of perturbations can better represent the practical prediction uncertainty.Based on this,the Grid-to-grid Probability(GP),NEP with different radii and EAS_NEP were compared for accuracy,forecast skill and other aspects of performance.The results showed that EAS_NEP can adjust the neighborhood radius adaptively according to the agreement between ensemble members and its radii tend to be lager for concentrated precipitation than dispersed precipitation.These dynamically adjusted radii not only avoid excessive smoothing and key information loss when the neighborhood radius is too large,but also eliminate the singular points caused by small radius and possess stepped spatial distribution with better continuity.In addition,quantitative evaluation results such as BS,FSS and ROC curves also confirm that EAS_NEP has improved forecasting skills compared to traditional methods,especially in the case of dispersed precipitation and high threshold situation.The results suggest that EAS_NEP has a good application prospect in the Meiyu frontal heavy rainfall events and can effectively improve the quality of probability forecast.
Keywords：probability forecastensemble forecastsensemble agreement scaleneighborhood ensemble probabilityMeiyu frontal heavy rainfall
Publication Date：2024-04-28
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 313-325 )