ECMWF集合预报产品对浙江汛期降水的预报性能评估

Performance Evaluation of ECMWF Ensemble Forecast Product for Precipitation in Flood Season in Zhejiang

利用2018和2019年汛期ECMWF集合预报系统输出的降水预报资料和浙江省内自动气象观测站的降水数据,通过RPS评分、Brier评分、可靠性分析和ROC分析等方法,评估了基于ECMWF集合预报的降水概率预报产品在浙江汛期降水中的预报性能。结果表明:(1)概率预报对多个量级降水的综合预报效果在0~24 h为最好,72 h以后开始明显变差;(2)分量级而言,概率预报对于从小雨到暴雨量级的降水都是有一定预报能力的,预报性能在1~4 d内较稳定;(3)系统对小雨的预报性能优于其他量级降水的预报,而对暴雨以上量级降水来说,预报性能迅速减弱;(4)对大雨以下量级降水,概率预报对于低频(高频)事件,给出过低(过高)的发生概率;而对暴雨以上量级降水全频率事件均出现高估。

Using the precipitation forecast data output by the ECMWF ensemble forecast system in the flood seasons of 2018 and 2019 and the precipitation data from automatic meteorological observation stations in Zhejiang Province, the forecasting performance of precipitation probabilistic forecasting product based on ECMWF ensemble forecast in flood season precipitation in Zhejiang Province was evaluated through methods such as RPS score, Brier score, reliability analysis and ROC analysis. The results showed that the probabilistic forecast had the best comprehensive forecast effect for multiple levels of precipitation from 0 to 24 hours, and it started to deteriorate significantly after 72 hours. In terms of component level, probabilistic forecasting had a certain forecasting ability for precipitation ranging from light rain to heavy rain, and the forecast performance was relatively stable within 1 to 4 days. the forecast efficiency of the system for light rain was better than that of other levels of precipitation, and for heavy rain and precipitation above heavy rain, the forecast performance rapidly weakened. For precipitation below heavy rain, probabilistic forecasts give low(too high) occurrence probability for low-frequency(high-frequency) events. All frequency events of precipitation above the torrential rain are overestimated.