| Different planet boundary layer parameterizations in WRF model are used to simulate the heavy rainfall in Yangtze-Huaihe basin during July 3-5, 2007.Precipitation and the thermal and dynamic structural characteristics in the boundary layer are compared to evaluate the model performance of simulating boundary layer characteristics during a Mei-yu event with different PBL schemes. Meanwhile, the characteristics of heat flux transport and turbulent kinetic energy (TKE) are analyzed and compared within the schemes. The results indicate that the use of different parameterization schemes has impact on the distribution and intensity of the rainstorm. The differences on precipitation rate and surface factors become larger as the rainstorm goes on. The differences on the vertical distribution of horizontal wind fields, vertical velocity and potential pseudo-equivalent temperature caused by the use of different schemes, have direct effect on the simulation of the rainstorm. The vertical distribution of heat flux transport and TKE, which are different from clear state are performed well by all schemes, with positive effect from wind shear and TKE transport, and negative from buoyancy. Among the schemes, BouLac provides the weakest budget equation terms while turbulent transport plays an important role in GBM's TKE budget. The characteristics of turbulent exchange performed by different schemes correspond well to those of TKE. Compared with other schemes,MYJ performed weaker TKE development and turbulent exchange, and weaker vertical transport of heat fluxes. GBM predicted weaker exchange within boundary layer, and much larger exchange coefficients above PBL. The vertical transport of heat flux at higher levels simulated by GBM performed obvious errors and has influence on the simulation of meteorological elements in precipitation area. Thus,further improvement is still needed. As to this case, the MYNN Level-3 scheme performs the best simulation. |
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