用三点法计算风场散度可能出现的重大误差及其原因分析

本文首先证明在天气诊断分析或物理量计算中常用的两种三点法计算散度公式都是相等的,继而证明用三点法计算风场散度可能存在重大的计算误差,其大小可达到中尺度天气系统的散度量级,接着对计算误差产生的原因进行了分析,证明这种误差是由于计算的三角形面积内风场出现了非线性分布所引起的,从而推论:当非线性分布的风场系统出现生、消或移动时,这种误差也会随之生、消或移动。

POSSIBLE SIGNIFICANT ERRORS ARISEN FROM THREE-POINT COMPUTATION OF DIVERGENCE AND THEIR CAUSES

In this paper, two kinds of 3-point equations of computing divergence, usually used in synoptic diagnoses or derivation of physical quantity, are shown to produce equivalent results. Values of divergence given by the 3-point methods may be accompanied with significant errors with the same order of magnitude as observed in mesoscale systems. They are contributed by non-linear distribution of triangular domains of flow fields computed. It is inferred that the errors generate, disappear or displace themselves with corresponding change in the non-linear distribution.