白天混合层顶部夹卷层厚度的特征研究

A study on characteristics of thickness of the entrainment zone above the mixed layer in the daytime

本文首先对Deardorff的一阶模型给予解释 ,在此基础上根据对流边界层湍流动能方程 ,分析机械湍流和对流湍流对边界层发展的贡献 ,提出一个新的速度尺度———混合层顶速度尺度 ,定义了全理查森数 ,给出夹卷层厚度的参数化方案 ,并用Boers和Elotanta的雷达观测数据进行验证 .参数化方案与实验数据符合得很好 .当夹卷层厚度表示为夹卷速度或夹卷理查森数的函数时 ,该函数曲线随边界层发展表现为磁滞回线形状现象 ,文中对此进行了解释 .

An explanation about the first-order model of Deardorff is given. Based on this explain, the turbulent kinetic energy equation is analyzed, and the contribution to evolution of the convective boundary layer is divided into two parts: buoyant production and mechanical production. Thereout, a new velocity scale, top velocity scale of mixed layer, is proposed. At the same time, the full Richardson number is defined. And a new parameterization of thickness of entrainment zone is concluded. It gives a good agreement with the data of Boers and Eloranta measured by lidar. When the entrainment zone thickness normalized by mixed-layer depth is ploted as a function of the entrainment Richardson number or the entrainment rate normalized by the convective velocity scale, the curve of the function behaves as hysteresis. A preliminary interpretation is made to this phenomenon.