Assimilation of Radar Radial Velocity in the Clear-Air Region and Its Impact on Forecasting

To investigate the impact of radial velocity assimilation in the clear-air region on forecasting, this paper conducted cycle assimilation experiments for short-duration convection and heavy rainfall forecasting using the latest classified raw radar data from the Meteorological Observation Centre of China Meteorological Administration. These experiments involve the assimilation of radial velocity in the clear-air region, alongside the assimilation of radar reflectivity factor and radial velocity in the precipitation region. The results show that as the cycle assimilation progresses, radial velocity in the clear-air region gradually influences the interior of the convective system, adjusting the thermal and dynamic conditions within the convection. This adjustment improves the coordination between various physical quantities, thereby improving the forecast skill of short-duration convection. Furthermore, the radial velocity in the clear-air region gradually affects the physical quantities in the precipitation region through the cycle of assimilation, thereby improving precipitation forecast skills. The study discloses that reasonable assimilation of radial velocity in the clear-air region can play an important role in pre-convection and precipitation forecasts.