Validation of the Canadian Regional Climate Model using spectral analysis

Spectra for various meteorological fields are computed using the two-dimensional Fourier transform technique on a limited-area grid of the Regional finite-element (RFE) model and the Canadian Regional Climate Model (CRCM). Limitations of removing the linear trend from the fields, and thereby removing the large-scale variance, are discussed. The spectra of difference fields are calculated, yielding the error variance for different scales.Spectral methods are used widely in the evaluation of global models. In this study, the same method is used for evaluating the CRCM in its ability to correctly reproduce the mesoscale systems in short-term integrations, when low-resolution GCM-like initial and lateral boundary conditions are provided. Two cases have been chosen for this study, the first one over the Montreal region and second one over the Mackenzie River Basin (MRB). It is found that the relative error variance growth at most scales, particularly the small scales, is less for the MRB region possibly due to the topographic forcing. In both cases and all experiments, the maximum relative error variance is found to be at a wavelength of about 350-km.Root mean square (rms) error and relative rms error for the geopotential height field for both cases are very small and show little or no growth, when scale decompositions are not made. However, the relative error variance when examined according to scale, show considerable differences. The relative errors at different scales show different growth rates and that of the meso-alpha and synoptic scales are found to be growing with time