Impacts of adding hydrometeor control variables on the radar reflectivity data assimilation for the 6–8 August 2018 mesoscale convective system case

Abstract

Hydrometeor information from radar reflectivity observations plays an important role in initializing convective-scale numerical weather forecast (NWP). The introduction of hydrometeor control variables facilitates rational division of the reflectivity information to obtain more accurate initial conditions of cloud and precipitation. Using the Weather Research and Forecasting (WRF) model, the effects of adding hydrometeor control variables on assimilation and forecasting are explored for a strong convective process occurring in Liaoning Province in this study. The results show that, compared with the experiment of no hydrometeor control variable, the presences of hydrometeor control variables are beneficial to the analyses of horizontal and vertical distribution of hydrometeors, which enables a better match of the analyzed structures with the reflectivity observations. Moreover, the reasonable hydrometeor distribution is able to reduce the generation of false echoes during assimilation. According to the results of the forecast experiments, using hydrometeor control variables tends to slow down the dissipation of hydrometeors, leading improved forecasting skills of the quantitative precipitation.