利用大涡模拟分析地表加热和动力作用对边界层结构的影响  

Analyze the Surface Thermodynamic and Dynamic Effects on the Atmospheric Boundary Layer Structure by Large Eddy Simulation

作　　者：张敏 梁捷宁[1] 张志达 张镭[1,2] ZHANG Min;LIANG Jiening;ZHANG Zhida;ZHANG Lei(Key Laboratory for Semi-Arid Climate Change of the Ministry of Education,College of Atmospheric Sciences,Lanzhou University,Lanzhou 730000,Gansu,China;Collaborative Innovation Center for Western Ecological Safety,Lanzhou University,Lanzhou 73000,Gansu,China)

机构地区：[1]半干旱气候变化教育部重点实验室,兰州大学大气科学学院,甘肃兰州730000 [2]兰州大学西部生态安全省部共建协同创新中心,甘肃兰州730000

出　　处：《高原气象》2022年第5期1232-1241,共10页Plateau Meteorology

基　　金：国家自然科学基金项目(41605005,41521004)。

摘　　要：大气边界层结构影响地气间物质能量交换、污染物扩散及人类健康.边界层结构受地表加热和动力作用影响显著,但实际观测中难以分离每种因素的影响,造成边界层结构和大气湍流参数化的困难.为此,利用中尺度天气模式WRF中的大涡模块WRF-LES,设置控制试验(Test1),地表热通量试验(Test2)、低层风切变试验(Test3)、地表粗糙度试验(Test4)及同时改变上述变量的试验(Test5),研究地表加热、低层风切变和地表粗糙度对平坦下垫面条件下的边界层结构的影响.模拟结果表明:(1)地表加热增强5倍使边界层升温,对流增强,夹卷层厚度增加120.8%,全边界层湍流动能增加45.7%,热力和动力边界层高度分别增大28.3%和29.9%.强烈的垂直混合作用有利于动量向下传递,使风速在边界层低层增大、中上层减小.(2)低层风切变增大0.5倍,使得热力和动力边界层高度分别增大11.9%和降低6%,夹卷层厚度增大31.2%,全边界层湍流动能增大25.7%.(3)粗糙度增加4倍,对湍流动能的影响主要集中在低层,动力边界层高度变化较小,但摩擦损耗作用使动力边界层内风速减小;同时,增加了边界层顶附近的夹卷作用,使边界层内位温升高.综合来看,地表加热和风切变对湍流动能和边界层结构的影响较为显著,而粗糙度的影响较小且主要集中在边界层低层.模拟结果能在一定程度上反映理想条件下边界层结构的变化特点,对气象因素影响污染扩散过程等问题有指示性意义.Atmospheric boundary layer structure affects the exchange of material and energy between the earth and air,the dispersion of pollutants and human health.The boundary layer structure is significantly affected by surface heating and dynamics,but it is difficult to separate the effects of each factor in practical observations,which causes difficulties in parameterizing the boundary layer structure and atmospheric turbulence.Therefore,using the large eddy module,WRF-LES,in the Weather Research and Forecasting Model(WRF),set up control test(Test1),surface heat flux(Test2),low-level wind shear(Test3),surface roughness(Test4)tests and test that change the above variables simultaneously(Test5)to investigate the effects of surface heating,low-level wind shear and surface roughness on the boundary layer structure on the flat surface.The results were as follows:(1)The surface heating,enhanced by 5 times,warmed up the boundary layer,enhanced convection,increased the thickness of the entrainment layer by 120.8%,increased the turbulent kinetic energy of the full boundary layer by 45.7%,and increased the height of the thermodynamic and dynamic boundary layers by28.3%and 29.9%,respectively.The strong vertical mixing facilitated the downward momentum transfer,which increased the wind speed in the lower boundary layer and decreased in the middle and upper boundary layers.(2)The 0.5 times increase in wind shear in the lower layer increased the thermodynamic and dynamic boundary layer heights by 11.9%and-6%,respectively,and increased the entrainment zone thickness by31.2%and the full boundary layer turbulent kinetic energy by 25.7%.(3)The 4 times increase in roughness affected the turbulent kinetic energy mainly in the lower layers.The change in height of the dynamic boundary layer was small,but the friction loss effect reduced the wind speed in the dynamic boundary layer.Meanwhile,it increased the entrainment effect near the top of the boundary layer,which increased the potential temperature in the boundary layer.In a comprehensive

关 键 词：大涡模拟 大气边界层结构 地表热通量 风切变 粗糙度 

分 类 号：P421.31[天文地球—大气科学及气象学]