THE UNCERTAINTY OF MESOSCALE NUMERICAL PREDICTION OF SOUTH CHINA HEAVY RAIN AND THE ENSEMBLE SIMULATIONS

In the context of non-hydrostatic MMS version we explore the impact of convective parameterization schemes on the uncertainty in mesoscale numerical prediction of South China heavy rain and mesoscale heavy rainfall short-range ensemble simulation by using two kinds of physics perturbation methods through a heavy rain case occurring in 8 June 1998 in Guangdong and Fujian Provinces.The results show the physical process of impacts of convective shcemes on heavy rainfall is that different latent heat of convective condensation produced by different convective schemes can make local temperature perturbation,leading to the differences of local vertical speed by the intrinsic dynamic and thermodynamic processes of atmosphere,and therefore,making difference of the timing,locations and strength of mesh scale and subgrid scale precipitation later.New precipitations become the new source of latent heat and temperature perturbation,which finally makes the dynamic and thermodynamis structures different in the simulations.Two kinds of methods were used to construct different model version stochastically, the first one is by using different convective parameterization and planetary boundary layer schemes,the second is by adjusting different parameters of convective trigger function in Grell scheme.The results indicate that the first ensemble simulations can provide more uncertainty information of location and strength of heavy rainfall and than the second.The single determinate predictions of heavy rain are unstable,physics ensemble predictions can reflect the uncertainty of heavy rain,providing more useful guidance and have higher application value.Physics ensembles suggest that model error should be under consideration in the heavy rainfall ensembles.Although the method of using different parameters in Grell scheme could not produce good results and how to construct the perturbation model or adjust the parameter in one scheme according to the physical meaning of the parameter needs further investigation.A limitation of the current study is the restriction to a single case and more cases will be addressed in the future researches.