Evaluation of the Canadian Numerical Weather Forecast in Support of the BAQS-Met Air Quality Modelling Effort

The accuracy of the meteorological forecast provided to a chemistry transport model (CTM) plays a determinant role in the performance of the latter. For numerical simulations covering the period of the Border Air Quality and Meteorology Study (BAQS-Met), the Canadian CTM AURAMS (A Unified Regional Air- quality Modelling System) used the meteorological outputs of the Global Environmental Multiscale model (GEM). BAQS-Met was conducted in Southwestern Ontario between June and August, 2007, with a period of intensive observations between June 20 and July 9. In support of AURAMS, both a regional version of GEM with a 15-km resolution, and a limited-area version with 2.5-km resolution were used to produce meteorological output. The performance of GEM during the intensive observation period will be presented. In particular, attention will be paid to mesoscale atmospheric phenomena such as convective precipitation, lake breezes, and daytime and nocturnal boundary layer formation which directly impact the CTM.