Abstract: The concept and application of blending height are introduced. Large-eddy simulations were conducted to study the blending height in convective boundary layers over heterogeneously heated surfaces. The influences of heterogeneous length, heterogeneous strength and wind speed on blending height were investigated. The results show that the blending heights are mainly determined by the heterogeneous length and wind speed, while less influenced by the heterogeneous strength. Blending height appears at the height where the spatial standard deviation of heat flux decreases to 5% of that on the surface and can be fitted as Z_b = 1/C_wm * w'θ'_sfc/Θ₀ * L^a_hetero/U^b, with a=1.266, b=0.854, C_wm=3.205×10^-3.

Key words: heterogeneous atmospheric boundary layer, surface fluxes, blending height, large-eddy simulation

摘要： 叙述了掺混高度的概念及运用。利用大涡模拟作为手段，研究了地表平坦但地表热通量非均匀情况下的掺混高度。考察了地表热通量非均匀性尺度、风速以及非均匀性强度对掺混高度的影响，发现掺混高度是否存在以及高度受非均匀尺度和风速大小的影响非常明显，受非均匀性强度的影响不明显。若规定掺混高度出现在垂直湍流热通量水平涨落的标准差减为地表感热通量标准差5％的高度，这时掺混高度可以拟合为：Z_b = 1/C_wm * w'θ'_sfc/Θ₀ * L^a_hetero/U^b，其中a=1.266，b=0.854，C_wm=3.205×10^-3。

关键词: 非均匀大气边界层, 地表通量, 掺混高度, 大涡模拟