东北冷涡数值预报系统建立与业务应用

Establishment of numerical prediction system for Northeast China cold vortex and its operational application

东北冷涡强降水一直是东北地区气象预报的难点和重点。从提高东北冷涡降水数值预报质量着手,选择模式中可能对东北冷涡强对流有影响的不同辐射方案、边界层方案和积云参数化方案等多种物理过程,对东北冷涡降水预报的性能进行批量试验;利用天气学检验方法,选择预报结果较好的RRTM长波辐射方案、Gayno Seaman边界层方案、Grell积云参数化方案和混合相湿过程显式方案等物理方案,组合建立了东北冷涡数值预报系统。经检验表明:系统对东北冷涡降水预报的水平较东北区域中尺度数值预报业务系统有所提高。同时利用天气学检验方法,从降水预报的强度、落区和移速等方面着手,评估东北冷涡数值预报产品对冷涡降水预报的性能和系统误差,得出降水强度易偏强、落区易偏西偏南和范围易偏小等定性结论,可直接应用于预报业务,取得了较好的应用效果。

Forecast of a heavy rain caused by the Northeast China cold vortex is always difficult but it is important to weather forecasting operation in the northeast China.Based on a number of tests using combination of different physical parameterization schemes,such as radiation,boundary layer and cumulus convection schemes available in numerical weather prediction model,the numerical prediction system for the Northeast China cold vortex has been built.The selection of parameterization is based on synoptic verification score that shows improvement in precipitation forecasting.The system includes physical schemes of long wave radiation,Gayno Seaman boundary layer,Grell cumulus parameterization and mixed phase humidity process.The result shows that the forecast accuracy of precipitation caused by the Northeast China cold vortex is higher using this system than using the operational system of meso-scale numerical forecast in the northeast China.At the same time,the influence of forecast products on the forecast capability and systematic error of precipitation caused by the Northeast China cold vortex are evaluated by a synoptic verification method in terms of density,falling areas and moving velocity of precipitation forecast etc..The evaluation indicates that the forecast precipitation intensity is stronger than the real;the forecast falling areas moves to west or south;the forecast scope is smaller than the real.These conclusions have been applied to operational forecast and led to better forecasting results.