The Hunan Limited-region Numerical Weather Prediction System And Numerical Experiments Of The System

Hunan Limited-region Numerical Weather Prediction System is based upon the Fifth-Generation PSU/NCAR Meso-scale Model (version 3.4), named MM5 which is a non-hydrostatic model. The initial and lateral boundary conditions of the system are generated from the output of the T213 model of the National Meteorology Center(NMC) and the routine observation data of surface and high levels. Following the configuration of MM5, the system consists of triple-nested grids with the resolutions 135km,45km and 15 km respectively ,and it utilizes 23 vertical full-sigma(o) levels. The system is run in a parallel environment of YH/CS16.Initialization and 48 hours forecasts for Hunan province areas can be completed in about 50 minutes by the YH/CS16.The operation experiments of the system are carried on from May 2002 and they can provide the forecasts of meteorological elements every 3 hours.Compared with real events, the results of the numerical experiment indicate that the model is able to reasonably predict the spatial and temporal distribution of precipitation and the model running is stable. The results also show that the precipitation forecast of the system is very sensitive to Cumulus Parameterization scheme, Planet Boundary Layer(PBL) scheme and Radiation scheme. For smaller meshes, the Grell Cumulus Parameterization scheme is better than the other three cumulus parameterization schemes that are also tested in the experiments. In addition, the precipitation prediction is strongly influenced by with or without PBL scheme in modeling. The comparisons among the experimental precipitation predictions of the MM5, T213 and HLAFS have shown that further improvements should be made on the HLAFS model. Diagnostic analyses are also applied to some physical parameters of output of control test.