A STUDY OF 1.5-ORDER CLOSURE TURBULENCE MODEL

Based on turbulence theory,a 1.5-order closure turbulence model is established.The model incorporating with the ground surface energy budget equation is constructed by means of a vertical one-dimensional(1-D)40-level grid-mesh.The numerical results reveal the 24-h evolution of the clear planetary boundary layer comparing with the Wangara boundary layer data of days 33-34.The model also takes into account some physical processes of radiative transfer and baroclinicity,revealing some important characteristics observed in the boundary layer,especially for the evolution of the mixed layer and low-level jet.The calculated results are in good agreement with the observational data.On the other hand,we also run the high-resolution model of the planetary boundary layer in the Mesoscale Model Version 4(MM4)with the same physical processes and initial conditions.The results show that the high-resolution model can not reveal those important characteristics as the 1.5-order closure model did.In general,it is shown that the 1.5-order closure turbulence model based on turbulence theory is better in rationality and reality.