中尺度非静力模式中常用气压分离技术的研究

A Study Concerning the Pressure Separation Technique Used for Current Nonhydrostatic Mesoscale Models

分析了气压分离和不分离 ,在几种不同的层结情况下 ,垂直气压梯度的截断误差。结果表明 :基本场取法不当 ,会引起巨大的截断误差 ,甚至和不分离时相当 ;反之 ,则较小。根据计算 ,提出了一种取基本场的方法 ,在一定条件下 ,可以使气压偏差的垂直梯度的截断误差比不分离时的相应误差小一个量级 ,从而 ,可以取较小的垂直分辨率。

The analysis of the truncation error in the vertical pressure gradient has been made with and without the pressure separation technique for different atmospheric stratifications. Computations demonstrate that the error introduced by the technique might be quite large, even equivalent to the case without separation, if the basic field is not properly chosen. Based upon the results a method for choosing the field is suggested. The truncation error in the vertical pressure departure gradient might be one order of magnitude less than that without the pressure separation under certain conditions. Therefore, it is permissible to choose lower vertical resolution in the separation case as compared to the case without separation.