A Consideration of Spectral Methods for Limited Area Models

[摘要] Tatsumi (1985) first applied a spectral method to a limited area forecast model using modified Fourier basis functions together with a transform method and the prescribed spectral coefficient of the additional basis function.Another limited area spectral method having the spectral coefficient of the additional basis function not prescribed but predicted, is formulated based on the Galerkin procedure, and compared with Tatsumi's method. Some merits of Tatsumi's method are discussed.It is shown that the use of a transform method in combination with a modified Fourier basis function leads to erroneous interaction coefficients and false energy generation.In addition, the Gibbs phenomenon for higher order derivatives and the effects of a boundary relaxation term in limited area spectral methods are demonstrated.

[学科分类] 大气科学