Experimentation And Application Research Of Doppler Radar Radial Velocity Data Assimilation In Three-dimensional Variational System

Doppler radar radial velocity data is assimilated into the mesoscale model WRF with WRF-3DVAR system, and its impact on rainfall and typhoon numerical forecasting is studied. Some results have been reached by comparing the assimilation and control tests of a torrential rain case of 2005.7.30 00:00~2005.73012:00 (UTC) and typhoon case of 2002.8.31 00:00~2002.9.1 00:00(UTC).(1) Results from the WRF 3D-Var assimilation test of the rainfall case show that the Doppler radar radial velocity data mainly adjust initial dynamical field. By the adjustment of wind-vector, divergence, vertical velocity, the precipitation's TS grade from the numerical forecast is improved.(2) Results from the WRF 3DVAR assimilation test of the typhoon case show that the Doppler radar radial velocity data adjusts the initial typhoon vortex to the right position by improving vortex structure .The numerical forecasts show that, the typhoon landfall prediction and precipitation are enhanced by the assimilation of Doppler radar radial velocity data.(3) Comparing with the control experiment, the assimilation experiment with high temporal and spacial resolution Doppler radar radial velocity data can provide more physical information during the rainfall and typhoon. Therefore, the assimilation of Doppler radar radial velocity data adjusts the atmospheric stability of the mesoscale model, and make the elements in the model more credible. Then, an enhanced initial field is prepared for numerical forecast.In this paper, three-dimensional variational assimilation tests results of Doppler radar radial velocity data in mesoscale model WRF show that the assimilation improved the initial field in model, and can reflect some mesoscale information which the control experiments can not find, and also its nonlinear characteristic information. Especially, different thermal and dynamic structure of rainstorm and typhoon could be well simulated by Doppler radar radial velocity data assimilation in WRF 3DVAR system. Doppler radar radial velocity data simulation will be useful in real time report of severe convective weather, and also have definite prospect in application .With the establishment of the new generation weather radar net in China in 2005, how to use the Doppler radar data effectively in mesoscale numerical forecasting in order to improve the forecast of severe weather and reduce its endanger, is an important issue for study at present and in future .