一个含地形的二阶矩湍流闭合的大气中尺度数值模式

AN ATMEOSPHERIC MESOSCALE NUMERICAL MODEL WITH SECOND-ORDER MOMENT TURBULENT CLOSURE OVER COMPLEX TERRAINS

建立了一个包含地形作用的二阶矩湍流闭合的二维大气中尺度数值模式，该模式不仅具有描述大气边界层及其内湍流结构的能力，而且还能很好地模拟非线性地形波、波破碎观象以及波破碎区内的湍流结构．

The downslope and upslope wind circulat}ons forced by orographicalthermal effects and the nonlinear mountain waves forced by finite-height orographicaldynamical effects have been successfully simulated long before (Orville(1964), Klemp andLilly (1978). However, the turbulent structure of the atmospheric boundary layer inmesoscale circulations and the turbulence appearing when highly developed nonlinearmountain waves breaking up are rarely simulated by numerical models (Physick(1989), Leeand Pielke (1989)).In currently used mesoscale numerical models, the parameterization scheme for thetUrbulence in the atmospheric boundary later is mainly used to represent the turbulent heattransfer and momentum friction. Therefore, the present mesoscale numerical models canwell simulate various mesoscale circulation systems but connot well describe the structureof the atmospheric boundary layer and especially the turbulent structure in the mesoscalesystems.The mixing of the turbulence appearing with lee waves breaking often makes the internal gravity waves from lower levels reflect at the interface of the wave-breaking region, andresult in the formation of a strong downslope windstorm (Clerk and Peltter, 1984). However, in the simulations on the situation with waves' breaking (Klemp and Lilly (1978),Pierehumbert and Wyman (1985), Clark and Peltter (1977), Durran (1986), IKawa (1989)),the introduced turbulent exchange term is often only the requirement of eliminating thecomputational instability caused blithe turbulent disturbance in the wave--breaking region.And the oversimplified parameterizations for turbulence inevitably make them not capableof discribing the turbulent structure. Based on the facts above and for the need of the study on mesoscale terrain flows andthe turbulent structures and effects in the flows, a two-dimensional atmospheric mesoscalenumerical model with secondorder moment turbulent closure and over comples terraing isdeveloped. Using this model, we successfully simulated the process of the convestiveboundary layer developing during 09:00-18:00 and corresponding turbulent structures onDay 33 of Wangara data, 'and also successfully simulated Klemp and Lilly (1978)'sfinite-amplitude mountain waves. Those not only conform the ability of the model simulating atmospheric boundary layer, the turbulence in the layer and orographical dynamicalforced airflows but also verify the dynamical frame of the model. Since the effect oforographical thermal forcing on the atmosphere is mainly realized by the turbulent transferin the atmospheric boundary, the ability of the model simulating orographical thermalforced airflows is indirectly verified by conforming the dynamical frame of the model andits ability of simulating tie structure of atmospheric boundary layer.In addition, the fact that the model well simulated the strong downslope windstorm onthe 11th of January, 1972 at Boulder in America further proves that the medel is also capable of simulating highly developed nonlinear mountain waves and the structure of the turbulence appearing with the mountain waves breaking.