CHANGES TO THE CANADIAN REGIONAL FORECAST SYSTEM - DESCRIPTION AND EVALUATION OF THE 50-KM VERSION

On 3 November 1993 a new higher-resolution version of the regional for ecast system was implemented into operations at the Canadian Meteorolo gical Centre. The changes include modifications to the regional data a ssimilation system and to the regional finite-element (RFE) forecast m odel. The main features of the new version of the RFE model include an increase in resolution from 100 to 50 km and to 25 sigma levels in th e vertical. The fields that describe the surface characteristics are g enerated directly on the 50-km grid of the model from high-resolution global geophysical datasets, yielding more derails and a much better d efinition of the orography and coastlines. The new RFE model also incl udes an improved package of physical parametrizations, notably for con densation and radiation processes. The major changes to the data assim ilation are a higher-resolution analysis, and the assimilation of humi dity profiles retrieved from satellite imagery. The new system is eval uated using performance statistics, and case studies are presented to highlight some of the benefits. These include more accurate analyses w ith a better fit to the data, and more detailed and precise forecasts, particularly for frontal zone structures, jet streams, moisture distr ibution and precipitation. The new physics package reduces the spinup of the model and the systematic errors in precipitation amounts, and g ives better thermal and hydrologic balances.