MULTI-SCALE TURBULENT PLANETARY BOUNDARY LAYER PARAMETERIZATION IN MESOSCALE NUMERICAL SIMULATION

Based on the multi-scale turbulent theory the sub-model of Multi-scale turbulent planetary boundary layer parameterization is set up by analyzing the relation of the gradient of average wind and the spectrum of turbulence in atmospheric boundary layer. Then the submodel is applied in MM5 to simulate the storm rainfall. Meanwhile the result of simulating is compared to that of the boundary layer parameterization of MRF and Blackadar originally included in MM5. After simulating the heavy rainfall between Changjiang and Haihe in Jun 22nd, 2002, it shows that the effect of the physical process in atmospheric boundary layer on mesoscale rainstorm is obvious because the change on vertical transportation of the momentum, heat and vapour near ground result in great difference in wind in lower level of MM5 and have effect on the birth and development of mesoscale synoptic system. In additional, the result also shows the ability to forecast large scale weather system is relied on the initial field and the dynamical structure of numerical model. The physical process has less effect on the forecast ability of large scale synoptic system, but influence obviously the forecast ability of mesoscale synoptic system. On the several rainstorm simulating, the effect caused by turbulent exchange between ground layer and each layer in boundary layer on wind field in lower layer is obvious especially in the area with complex topographic and surface characters. Therefore, it has long-range future to apply Multi-scale turbulent boundary layer parameterization on simulating the mesoscale synoptic system. In general, it is feasible to apply Multi-scale turbulent theory on mesoscale numerical simulating. Introducing the turbulence σ_w, σ_T and the sizes of eddy make it possible that the vertical motion in atmospheric boundary layer not only directly relate to dynamic structure of ground layer, for example Z₀, but also relate to the nonuniformity of heat structure in ground layer and every layer in atmospheric boundary layer, and it is just the advantage of Multi-scale turbulent boundary layer parameterization.