干湿对流大气边界层大涡模拟及模式收敛性分析  

Large-Eddy Simulation of Dry and Moist Atmospheric Boundary Layers and Analysis of the Model Convergence

作　　者：张艺馨 彭新东[1,2] ZHANG Yixin;PENG Xindong(State Key Laboratory of Sever Weather,Chinese Academy of Meteorological Sciences,Beijing 100081,China;Division of Numerical Model Techniques,China Meteorological Administration Earth System Modeling and Prediction Centre,Beijing 100081,China)

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室,北京100081 [2]中国气象局地球系统数值预报中心模式技术室,北京100081

出　　处：《高原气象》2024年第6期1559-1572,共14页Plateau Meteorology

基　　金：国家自然科学基金项目(42375153,42075151)。

摘　　要：利用中尺度天气研究预报模式WRF中的大涡模拟(LES)版本对理想干对流边界层和浅对流云覆盖的海洋性大气边界层结构和湍流输送特征进行大涡模拟,并通过不同水平分辨率大涡模拟结果分析了大涡模式的收敛性。结果表明:不同分辨率大涡模式模拟的干对流边界层高度约为1.15 km,位温、水汽混合比和水平风速等平均变量在边界层内均匀分布,但在近地层和边界层顶垂直梯度较大。随模式分辨率的提高,可分辨出更精细的对流泡结构,夹卷层的位温方差增大,模拟的混合层平均物理量均匀分布更接近地面,与粗分辨率下大涡模拟的偏差主要集中在边界层下层和逆温层附近,解析热通量增加,但总热通量保持不变。不同于干对流边界层,在有浅对流云覆盖的边界层内,混合层高度较低,混合层内平均气象要素垂直廓线和方差或通量廓线与干对流边界层内相似,低层混合层内平均气象要素呈垂直均匀分布,但由于混合层以上存在条件不稳定云层,云层内有正热通量和正垂直湍流动能,而混合层顶到浅对流云底部为负热通量,反映了混合层顶夹卷过程作用。较粗分辨率的大涡模式增加了逆温层顶、近地层平均风速和通量的模拟偏差。湍流发展旺盛的干对流边界层,大涡模式在约40 m的水平分辨率上收敛,而对混合层高度较低的浅积云覆盖边界层,模式则在约30 m水平分辨率上收敛,具有较低混合层高度的大气边界层需要更高分辨率的大涡模式描述。By using the large eddy simulation(LES)version of the Weather Research and Forecasting(WRF)model,vertical structure and the feature of turbulent transportation of shallow-convective-cloud-topped atmospheric convective boundary layer was simulated in addition to the idealized dry convective boundary layer on oceanic surface.Numerical convergence of LES model was analyzed with the model results in different resolutions.The results showed that the dry convective boundary layer was vigorous.Approximately 1.15 km of the planetary boundary layer height was simulated with the LES in different resolutions.Vertical uniform structure of the averaged potential temperature(θ),mixing ratio of water vapor(qv)and horizontal wind(u and v)were shown in the idealized dry convective boundary layer but with large vertical gradients in the near surface layer and the top of the boundary layer.Higher resolution model resolved more detailed structure of convective bubbles within the dry convective boundary layer,larger variance of potential temperature in the entrainment layer,vertical uniform distribution of the averaged quantities within the simulated mixed layer extending more closing to the surface,and the errors in LES model under coarse resolution were mainly concentrated in the lower boundary layer and near the inversion layer.The higher resolution LES model showed larger resolved sensible heat flux while the total flux remained.In the case of shallow-convective-cloud-topped boundary layer,obvious different boundary layer structure was displayed in comparison with that of the dry convective boundary layer.Conditionally unstable layer existed over the mixing layer,and mixing layer height dropped.Vertical profiles of averagedθ,qv,u and v showed similar structure in the mixing layer as that in the convective boundary layer.The averaged meteorological quantities in the lower mixing layer were uniformly distributed in vertical direction.In the cloudy layer,however,positive heat flux and vertical turbulent kinetic energy appeared.Neg

关 键 词：大气边界层 大涡模拟 收敛性 湍流动能 层积云 

分 类 号：P435[天文地球—大气科学及气象学]