有限区域气象场的谱展开

SPECTRAL EXPANSION OF METEOROLOGICAL FIELDS IN A LIMITED DOMAIN

本文讨论了有限区域内气象场的谱展开方法。由于有限区域存在侧边界,其上的气象场量值并无周期性,因此,在有限区域内将气象场量按谱方法展开时,需要作特殊的处理。本文利用侧向边值的线性扣除法,将气象场作线性变换,使侧边界值为零值,将变换后的气象场量作谱展开,并推导出导数的求导公式。变换时利用FFT方法,最后用理想函数作了检验,结果表明,本方法具有较高的计算精度,可用于气象场的谱分析,滤波和物理量的诊断分析中。

A spectral expansion method for meteorological fields in a limited domain is discussed in this paper. Values of a meteorological field at two boundaries of a limited domain are usually nonperiodic. Therefore special treatments are necessary when the spectral method is used. In this paper a linear transformation makes the boundary values equal to each other and become zero, then the spectral expansion can be utilized. The first-order and also the second-order derivatives of the expansion form are obtained. With some ideal functions tests on the accuracy of the method are made and show that the method has higher accuracy and can be used in spectral analysis, filtering and calculation of physical quantities of meteorolg-ical fields,