一个改进的湍流垂直扩散过程参数化方案

A IMPROVED PARAMETERIZATION SCHEME OF VERTICAL TURBULENT DIFFUSION

中文关键词:  湍流扩散  参数化  数值模式

英文关键词:Turbulent diffusion  Parameterization  Numerical models

中文摘要:

      研究了数值天气预报模式中次阿格湍流垂直扩散过程的参数化问题。以Bougeault和Lacarrère(1989)的参数化方案为基础,改进了处理湍流混合长的方法,使湍流混合长和热力混合长分别依赖于基本气流的静力稳定度和风场切变。新方案的基本思路是把Von Karman(1930)提出的动力(风场切变)湍流扰动假设与BL-89方案提出的热力(静力稳定度)湍流扰动假设结合在一起,强调了大气的热力结构、动力结构和湍流动能对湍流混合过程的共同影响。新方案和BL-89方案的二维对比数值试验结果表明,在大气处于静力较稳定而风场切变明显条件下的湍流扰动表现能力方面,新方案比原方案有明显的改进。

英文摘要:

      The parameterization problem of vertical turbulent diffusion in a Numerical Weather Prediction (NWP) model was addressed in this paper. Based on the turbulent scheme of Bougeault and Lacarrere (1989, referred as BL-89 scheme hereafter),the method for dealing with Turbulent Mixing Length (TML) was modified so that the dynamic TML and thermodynamic TML depend respectively upon the atmospheric static stability and wind shear. The basic idea of the new scheme is to combine the dynamic turbulent approach (wind shear) of Von Karman (1930) and the thermodynamic approach (static stability) of BL-89 scheme. It emphasis the comprehensive impacts of the atmospheric dynamic structure. thermodynamic structure and turbulent energy on the turbulent mixing. In comparison of the new scheme with the BL-89 scheme. it was concluded that under the conditions of stronger atmospheric static stability and wind shear. the new scheme has a better capability of representation of turbulent activities.