多物理过程对流可分辨集合预报中不同方案在四川盆地东部降水预报效果评估

Evaluation of Precipitation Forecasts with Different Parameterization Schemes of Multi-Physical Convective-Permitting Ensemble System in Eastern Sichuan Basin

利用四川盆地东部站点观测数据和对流可分辨集合预报系统模式数据,评估了该系统各成员及不同物理过程参数化方案在2017—2019年4—9月的降水预报效果。结果表明:概率匹配平均和集合平均相比于各个集合成员存在明显的预报优势。Kain-Fritsch(KF)和Betts-Miller-Janjic(BMJ)积云参数化方案的预报效果相对较好,Grell 3D ensemble(G3)方案在48 h之后的临界成功指数(critical success index,CSI)评分偏低。Thompson和Morrison微物理参数化方案对小雨量级降水的预报效果较好,WRF Single-Moment 6-class(WSM6)方案对中雨量级降水的预报效果较好,三种方案对大雨和暴雨量级降水的预报效果相当。Mellor-Yamada-Janjic(MYJ)和Mellor-Yamada-Nakanishi-Niino(MYNN)边界层方案的CSI评分相对较高,Yonsei University(YSU)方案在48 h之后的预报评分较低,但YSU方案多和G3方案搭配使用,其评分偏低主要受G3方案影响。各参数化方案均能把握四川盆地东部的降水分布特征,但对华蓥山、武陵山和大娄山的降水存在高估,对渝中至渝东北的降水存在低估。四川盆地东部的降水预报对积云参数化方案最为敏感。将一个成员的G3方案调整为KF方案后,降水预报评分显著提升,且集合离散度有所增加,概率预报技巧得到提高。

Based on the precipitation forecast data of convection-permitting ensemble prediction system and observation data from April to September in 2017,2018 and 2019,the effects of 24 h accumulated precipitation forecast of ensemble members in eastern Sichuan Basin are verified and compared,and the performance of different physical parameterization schemes is further discussed.Results show that the ensemble average forecast and probability matching forecast have obvious advantages over the ensemble members.The prediction performance of Kain-Fritsch(KF)and Betts-Miller-Janjic(BMJ)cumulus parameterization schemes is relatively good,while the critical success index(CSI)score of Grell 3D ensemble(G3)scheme is relatively low after 48 h.Thompson and Morrison microphysical parameterization schemes are better for light rain than WRF Single-Moment 6-class(WSM6)scheme,while WSM6 scheme is better for moderate rain,and there is no significant difference in the CSI scores of heavy rain and rainstorm among the three schemes.The CSI score of Mellor-Yamada-Janjic(MYJ)and Mellor-Yamada-Nakanishi-Niino(MYNN)boundary layer schemes is higher than that of Yonsei University(YSU)scheme,especially after 48 h.However,YSU scheme is mostly used in combination with G3 scheme,so its low score is mainly affected by G3.The precipitation distribution characteristics of all these schemes are similar to those of observation,but the false strong rain belt is predicted in Huaying Mountain,Wuling Mountain and Dalou Mountain,and the precipitation from the middle to the northeast of Chongqing is underestimated.The precipitation forecast in eastern Sichuan Basin is most sensitive to cumulus parameterization scheme.After adjusting one member’s G3 scheme to KF scheme,not only the forecast score is significantly improved,but also the ensemble spread is increased,and the skill of probability forecast is improved.