An economical assimilation scheme for radar reflectivity in non‐convective region to suppress spurious precipitation

Abstract

AbstractIncreasing convection information in initial field and weakening spurious convection information are hot topics in numerical weather prediction. How to economically assimilate radar reflectivity in the non‐convective region (NCR) is the focus of this study. This study proposes a new assimilation scheme for the two‐dimensional (2D) composite reflectivity in NCR through the ensemble square‐root filter method. A single‐column observation test and two convective cases are studied to verify the assimilation effect. Three experiments are designed for each test, including a control experiment (Exp_CTL) that only assimilates convective reflectivity and two assimilation experiments that assimilate reflectivity in NCR (one assimilates 3D weak reflectivity [Exp_RF] and the other assimilates 2D composite reflectivity [Exp_CRF]) based on the Exp_CTL. The results of real‐case studies show that the new scheme has two clear advantages. One is that it can save approximately three quarters of the assimilation workload. The other is that the new scheme has the most significant effect on weakening spurious convection and decreasing the false alarm ratios of precipitation and reflectivity.