DEVELOPMENT OF THE 35-KM VERSION OF THE CANADIAN REGIONAL FORECAST SYSTEM

A new, higher-resolution version of the regional forecast system was i mplemented into operations at the Canadian Meteorological Centre durin g 1995. The new version of the regional finite-element forecast model is run at 35-km resolution in the horizontal and 28 sigma levels in th e vertical (instead of 50-km and 25 levels in the previous operational version), with a more advanced physics package. The improved physical parametrizations feature the following: 1) modifications to the treat ment of surface surface processes; 2) changes to the surface layer for mulation; 3) an explicit cloud scheme following Sundqvist for stratifo rm precipitation; 4) Fritsch-Chappell scheme for deep convection. The new regional forecast system also includes a pseudo-analysis of initia l soil moisture content based on model error feed-back. Both objective and subjective evaluations on case studies and in the parallel runs s howed improved performance with the new 35-km model. The main points f rom these verifications indicated a significant reduction of the moist bias near the surface, improvements in the predicted surface temperat ures and the diurnal cycle, better forecasts of convective precipitati on, and more realistic surface wind forecasts, especially over complex orography due to the increased resolution. The new predicted cloud pa rameters permit a better representation of the cloud-radiation interac tions that are important for the atmospheric energy balance, especiall y at the surface.