Surface Heterogeneity Effects on Regional-Scale Fluxes in Stable Boundary Layers: Surface Temperature Transitions
Surface Heterogeneity Effects on Regional-Scale Fluxes in Stable Boundary Layers: Surface Temperature Transitions
复制标题
表面异质性对稳定边界层区域尺度通量的影响：表面温度转变
DOI：
10.1175/2008jas2668.1
复制
发表时间：
2009
影响因子：
3.1
通讯作者：
F. Porté
中科院分区：
文献类型：
--
作者：
R. Stoll;F. Porté
采用大涡模拟方法，结合新近发展的动态亚格子尺度模式，研究了稳定边界层(SBL)中非均匀表面温度分布对区域尺度湍流通量的影响。对连续湍流SBL进行了模拟，表面温度以流向转变的形式增加了表面非均质性。用相当于均匀边界层高度一半到两倍的斑块长度尺度研究了6K和3K斑块之间的温差。地表温度不均匀对平均风速和位温廓线以及地表热通量分布有重要影响。增加补丁之间的温度差会导致平均表面热通量的减小，而边界层中的平均位温相应地增加。模拟结果还被用来检验现有的非均匀地形上的平均地表通量模型。测试的模型不能完全表示平均湍流热通量，将区域划分为均匀的子区的模型严重低估了表面温度相对较低的斑块上的热通量大小。在此基础上，提出了一种新的基于局部相似理论的参数化方法。新的公式被发现纠正了对冷斑的偏差，从而改进了平均表面热通量计算。
Large-eddy simulation, with recently developed dynamic subgrid-scale models, is used to study the effect of heterogeneous surface temperature distributions on regional-scale turbulent fluxes in the stable boundary layer (SBL). Simulations are performed of a continuously turbulent SBL with surface heterogeneity added in the form of streamwise transitions in surface temperature. Temperature differences between patches of 6 and 3 K are explored with patch length scales ranging from one-half to twice the equivalent homogeneous boundary layer height. The surface temperature heterogeneity has important effects on the mean wind speed and potential temperature profiles as well as on the surface heat flux distribution. Increasing the difference between the patch temperatures results in decreased magnitude of the average surface heat flux, with a corresponding increase in the mean potential temperature in the boundary layer. The simulation results are also used to test existing models for average surface fluxes over heterogeneous terrain. The tested models fail to fully represent the average turbulent heat flux, with models that break the domain into homogeneous subareas grossly underestimating the heat flux magnitude over patches with relatively colder surface temperatures. Motivated by these results, a new parameterization based on local similarity theory is proposed. The new formulation is found to correct the bias over the cold patches, resulting in improved average surface heat flux calculations.