局地热源上大气边界层及其与自由大气相互作用的理论研究

本文利用二维高阶矩湍流闭合的中尺度数值模式,模拟了局地加热源上大气边界层的湍流结构,讨论了大气边界层与自由大气之间的相互作用,并由此亦使人们在海风消失时常常观测到的“风通（ｂｏｒｅ）”现象得到解释。

Theoretical Study on Atmospheric Boundary Layer and the Interaction with Free Atmosphere over Local Heating

In this peper, the locally thermal circulations are simulated by the mesoscale numerical model with higher-order turbulent closure. The atmospheric boundary layer(ABL) and its turbulent structure in locally thermal circulations and fields of winds and temperatures in the corresponding free atmosphere( FA) are discussed,The main conclusions are as following:(1) With local heat source strengthening, the ABL rapidly develops upwards, especially over the center of the heat source, and at the middle of the ABL,there occurs a maximum value of turbulent kinetic energy. At the same time the upward turbulent heat transfer is the strongest,(2) In the ABL over the local heat source, there are horizontal convergence flows at the middle and lower part and horizontal divergence flows at the upper part of the ABL. Therefore, the wind field in the ABL is apparently affected by the feedback of the FA, However, under the forcing of the local heat source, the disturbed flows in the FA are mainly controlled by the vertical motion forced at the top of the ABL.(3) When local heat source is tending to disappear, the disturbed fields in the FA are not controlled any more by the forced upward motion in the ABL but regulate themselves to the wave structure. Meanwhile, the convergence flows in the ABL over the center of the original local heat source are also obviously suppressed by the disturbed waves in the FA and probably make the disturbed fields in the ABL become thewave structure, too. From this, the "bore", appearing when sea breeze disappears, can be explained.