Simulation of Satellite Passive Microwave Observations in Rainy Atmospheres at Meteorological Service of Canada

In the present study, a research version of the Meteorological Service of Canada (MSC) Global Environmental Multi-Scale (GEM) mesoglobal weather forecast model is evaluated by comparing simulated SSM/I brightness temperatures (Tbs) with observed ones. Several comparisons based on two-15-day periods, one in winter and one in summer, have been done. Results are compared to those obtained by [F. Chevallier, P. Bauer, Mon. Wea. Rev., vol.131, p.1240-55 (2003)] for a study conducted on the European Centre for Medium-Range Weather Forecast (ECMWF) model. The overall performance of the GEM model is similar to that of the ECMWF model. The model appears to simulate with realism the large-scale rainy systems but with frequent mislocations. Moreover, the model has a tendency to produce intense small-scale precipitating areas that are not observed. The frequency of cloud and rain occurrences is overestimated by the model. The model has the best skill at simulating the 22 GHz Tbs indicating that the simulated water vapour is realistic in cloudy areas. Finally these results are encouraging enough to continue investigation on the assimilation of brightness temperatures in cloudy and rainy skies at MSC