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On 3 November 1993 a new higher‐resolution version of the regional forecast system was implemented into operations at the Canadian Meteorological Centre. The changes include modifications to the regional data assimilation system and to the regional finite‐element (RFE) forecast model. The main features of the new version of the RFE model include an increase in resolution from 100 to 50 km and to 25 σ levels in the vertical. The fields that describe the surface characteristics are generated directly on the 50‐km grid of the model from high‐resolution global geophysical datasets, yielding more details and a much better definition of the orography and coastlines. The new RFE model also includes an improved package of physical parametrizations, notably for condensation and radiation processes. The major changes to the data assimilation are a higher‐resolution analysis, and the assimilation of humidity profiles retrieved from satellite imagery. The new system is evaluated using performance statistics,...

A simple gravity wave drag parametriiation over mountainous terrain is tested for its ability to reduce the systematic errors of medium‐range weather forecasts. Following Boer et al. (1984), this parametrization is a function of the low‐level wind speed and stability, the local Froude number, and the variance of the subgrid‐scale orographie features. A comparison study of ten 7‐day forecasts obtained with envelope orography, wave drag or standard orography, shows that wave drag is as effective as envelope orography in reducing the systematic errors. A further comparison where the combined effects of the wave drag and that of a complementary enhanced orography (that is one that includes only the subgrid‐scale elements not treated separately by wave drag) are taken into account shows this latter approach to be the most promising in reducing orographically‐related systematic errors.

The systematic error of a large ensemble of 72 ‐h forecasts, as produced by the Canadian Meteorological Centre's spectral model, is studied with particular emphasis on its seasonal and spatial character. By decomposing the error into wavenumber space, we show that most of the error manifests itself in the long planetary waves. We find that the model displays a large systematic error in zonal wavenumber one, which systematically moves westward during each integration.