修正的ECMWF质量通量积云参数化方案的预报试验   总被引：6，自引：1，他引：6  

陈伯民  陈玉春  苏志侠  钱正安 《高原气象》1996,(1)

用一个有限区域业务预报模式，以１９９５年７—８月西北地区几次大范围的降水天气过程为试验个例，对经过修改的ＥＣＭＷＦ质量通量积云参数化方案和模式中的原Ｋｕｏ型积云参数化方案进行了共１３例４８ｈ的批量对比预报试验。结果显示：质量通量方案能给出比Ｋｕｏ型方案更合理的积云降水落区；质量通量方案对模式预报≥１０．０ｍｍ的降水有一定的改进，并提高了各种降水等级的预报效率评分值  相似文献   

Modelling Boundary-Layer Clouds With a Statistical Cloud Scheme and a Second-Order Turbulence Closure     

K. Abdella  N. McFarlane 《Boundary-Layer Meteorology》2001,98(3):387-410

We present a second-order turbulence model for the cloudy planetary boundary layer (PBL), which includes a statistical scheme of the sub-grid scale condensation. The model contains prognostic equations for the turbulent kinetic energy, total water, and liquid water temperature, the latter two being assumed to be conservative variables. Using these conservative thermodynamic variables the condensation process is formulated as a function of the departure of the total water from saturation and its variance. The computation of the variance requires second moment correlations which are modelled through the parameterization of the third-order moments using a convective mass-flux formulation. The inclusion of these third moments and new assumptions on heat flux transport lead to a nonlocal turbulence scheme with counter-gradient effects. The final form for the heat flux turns out to be a linearized version of a previously established result. For the statistical cloud formulation, a linear combination of a Gaussian and a positively skewed distribution function is used with a modified liquid water flux expression to account fornon-Gaussian behaviour.The effect of the turbulence scheme on the boundary-layer cloud structure is discussed and the performance of the model is tested by comparing it against the large eddy simulation (LES) of the undisturbed period of the Atlantic Stratocumulus Transition Experiment (ASTEX). The model is able to produce both mean and turbulent quantities that are in reasonable agreement with the LES output of ASTEX.  相似文献   

Third-Order Moment Closure Through A Mass-Flux Approach     

K. Abdella  A.C. Petersen 《Boundary-Layer Meteorology》2000,95(2):303-318

The parameterization of the third moments, the flux of the heat flux and the flux of the potential temperature variance, is considered. It is shown that present parameterizations of these moments using the mass-flux approach with a `top-hat' profile assumption lead to a significant underestimation, resulting in an inaccurate representation of second moments in the convective boundary layer. It is also shown that the underestimation is a result of the `top-hat' profileassumption in which the sub-plume contributions to the total fluxes are ignored. By including these contributions a new parameterization is proposed, whichsatisfies the physical requirements of symmetry andrealizability, and gives results that are in fair agreement with thelarge-eddy simulation data.  相似文献