Numerical Simulation of a Freezing-Rain Process in Beijing Capital International Airport and the Mechanism for Its Formation

In order to investigate the possible mechanism of freezing rain process, the WRF model (Weather Research and Forecasting) was used to simulate a freezing-rain process occurred on 31 Jan 2013 in the area of the Beijing Capital International Airport. The NECP reanalysis data, the Black Body Temperature (TBB) of FY-2E, the daily average cloud height data of FY-3A are used to verify the model simulation. Major conclusions are as follows:1) The cloud top temperature of the simulation is consistent with TBB of FY-2E. During the freezing rain process, the cloud top temperature varied between 0--6℃, and the simulated vertical distribution of the hydrometeors agree well with observations. According to the cloud top height derived from FY-3A observations, it is found that the cloud top in the freezing-rain process basically remained at around 3 km, and the clouds contained less microphysical solid contents. 2) Observed cloud top temperature and height and the simulation results show that this is a typical warm freezing rain process. This result indicates that the mechanism for the formation of freezing rain in northern China may not be single. Ice-crystal processes and warm-rain processes may simultaneously exist during the formation of freezing rain.