基于数值模式产品的广西冰雹客观预报方法研究

利用2012—2016年广西重要天气报(WS报)和信息员上报的冰雹实况,以及欧洲中心(ECMWF)0.125°×0.125°的逐6 h再分析资料,分析不同天气背景下广西历史冰雹个例发生前后关键物理参数的特征及其变化。从不稳定能量、水汽条件、对流触发条件、垂直风切变、0℃层高度、-20℃层高度等方面归纳总结广西冷空气影响冰雹过程及暖区冰雹过程的预报指标,应用预报指标动态调整的配料法,分别建立冷空气影响冰雹过程和暖区冰雹过程的广西分类冰雹客观预报方程。利用方程对2017—2018年2—6月广西冰雹进行试报,结果表明该方程对广西冰雹天气有一定的预报能力,其中对大范围冷空气南下触发的冰雹过程较暖区发生的冰雹天气过程预报更为准确,但也存在较大范围的空报,空报区域基本与雷暴大风天气落区对应,具有一定的警示作用。

Study of Objective Forecast Method of Guangxi Hail Based on Numerical Model Product

The characteristic and variation of key physical quantities before and after historical hail processes under different synoptic background in Guangxi were analyzed based on severe weather observation and social reports in Guangxi,and reanalysis data at 6 h intervals with 0.125°×0.125°spatial resolution from the European Centre for Medium-Range Weather Forecasts(ECMWF)during 2012-2016.Forecasting indices of hail under frontal condition and non-frontal condition were found respectively,which mainly focused on instability energy,water vapor,triggering,vertical wind shear and the height of 0℃,-20℃layer.Based on the ingredients-based methodology with dynamic forecast indices,objective forecasting equations for each condition were set up and applied from February to June during 2017-2018.The inspection showed that the equations were effective to hail forecasting in Guangxi.The forecast accuracy was higher under large-scale frontal condition than that under non-frontal condition.Although the hail area forecast had a high false alarm rate,but it mostly overlapped with thunderstorm gale region,so it was available for early warning.