山东一次低涡切变型暖区暴雨大范围漏报原因

Cause of a Large-Scale Forecast Failure of a Warm-Sector Rainstorm of Low Vortex Shear Type in Shandong Province

低涡切变型暖区暴雨预报是山东省暴雨预报中的一个难点问题,2021年8月30—31日山东中部及半岛地区出现大范围暖区暴雨天气,主观预报强度偏弱,范围偏小,暴雨出现大范围漏报。本文利用常规数值模式资料、地面观测资料、雷达资料等对漏报原因进行回顾,结果表明:对大气综合稳定度特征、边界层暖锋锋生特征、超低空急流、低空急流与高空急流垂直相互作用,以及边界层和中层弱冷空气的作用判断不够全面,在环境场已经发生变化的情况下,仍然用前期短时间内模式检验结果作为未来模式降水订正的依据等,可能是导致此次暖区暴雨过程预报不足的主要原因;在今后类似预报中应全面分析条件不稳定、对流不稳定和对称不稳定特征,关注边界层假相当位温密集带和边界层暖锋锋生特征,考虑急流垂直三维结构以及不同高度弱冷空气的作用,并应依据环境场的变化特征,判断数值模式暴雨预报性能,进行合理的动态订正。

Forecasting the warm-sector rainstorm of low vortex shear type is a difficult point in the rainstorm forecasting operation of Shandong Province.From 30 to 31 August 2021,a large range of warm-sector rainstorm occurred in the central and peninsula area of Shandong Province,but the forecasted rainfall intensity was weaker and affected area was smaller than the observed,resulting in the missing report of the rainstorm in a large scale.Based on numerical forecast products,conventional surface and upper-air observation data,Doppler radar data,we review the forecast errors of this warm-sector rainstorm event.The findings suggest that,during the forecasting process,the symmetric instability characteristics of atmosphere,the characteristics of warm front frontogenesis in the boundary layer,the vertical interactions of ultra-low level jet,low-level jet and upper-level jet,and the function of weak cold air in the boundary layer and middle layer failed to be judged completely by forecasters.In the case that the environmental field had changed,the model products in a short time in the previous period were still used as the basis for the precipitation correction of the model results.This may be the critical reason for the insufficient forecast of this warm-sector rainstorm process.In the future,when forecasting the similar warm-sector rainstorms,forecasters should comprehensively analyze the characteristics of conditional instability,convective instability and symmetric instability,and also pay attention to the characteristics of boundary layerθse dense zone and the warm front frontogenesis characteristics of the boundary layer.Moreover,the vertical three-dimensional structure of jet stream and the role of weak cold air at different heights should be considered,and the overestimation or underestimation of rainstorm forecast by the numerical models should be judged according to the environmental field features,and then reasonable dynamic model correction should be carried out.