雷达径向风速同化对台风麦莎模拟的影响

The Effects of Radar Radial Velocity Data Assimilation on the Simulation of Typhoon Matsa

本文应用WRF-3DVAR系统同化多普勒雷达径向风速资料,并利用WRF模式对台风麦莎(2005年8月6日00时至7日00时)进行数值模拟,以此检验多普勒雷达径向风速资料在改进模式初始场及提高台风路径和降水预报准确度等方面的应用效果及意义,探讨不同同化时间间隔对同化效果的影响。通过对比同化试验和控制试验发现:雷达径向风速资料能通过调整初始风场结构,改进对台风结构的模拟,从而提高模式对台风麦莎的路径、强度和降水的模拟能力;雷达资料信号在进入模式后有一定的时效性,在一定程度上缩小同化时间间隔有助于提高同化效果。

Data assimilation plays an important role in numerical weather prediction. Radar radial velocity data with high spatial and temporal resolution are one of the most useful data in data assimilation. In order to investigate the effects of radar radial velocity data and data assimilation interval on typhoon Matsa＇s track and precipitation, the direct assimilation procedure of Doppler radar radial velocity data using the three-dimensional variational （3DVAR）data assimilation method is set up for the Weather Research and Forecasting （WRF） model. Five numerical experiments are conducted for the simulation of typhoon Matsa （2005）. a control run （CTL） without data assimilation, and four assimilated runs （ASSG, ASSGR, ASS6h, and ASS3h）. Comparing the assimilation experiments （ASSG and ASSGR） and the control one （CTL） shows that, the radar radial velocity data can tune the typhoon structure and hence improve the simulation of typhoon Matsa＇s track and precipitation. During the first 12 hours, the deviation between simulation and observation of the Matsa position decreases by 19.3 km and 25.9 km for ASSG-run and ASSGR-run, respectively. Although the simulated 12-hour accumulated precipitations are both overestimated by the ASSG and ASSGR runs in Ningbo, Zhoushan, and Jiaxing regions, it is much better than that by the CTL run. In order to investigate the effects of data assimilation interval on typhoon Matsa＇s track and precipitation, three as- similated experiments with different data assimilation intervals are compared. Results show that small data assimilation interval can improve the result of the numerical experiment.