Tuesday, 31 July 2001
A Mesoscale Model for Global Medium-Range Weather Forecasting in Canada
In an effort to improve medium-range weather forecasting in Canada, a mesoscale version of the Global Environmental Multi-scale (GEM) model is now being developed in collaboration with the Canadian Meteorological Center. The horizontal resolution of this new configuration is on the order of 35-40 km, with about 45-50 levels in the vertical. The aspect of this work we feel is most innovative concerns the clouds and condensation physics, which is believed to be more appropriate for mesoscale models, i.e., with horizontal resolutions of a few tens of kilometers. The Kain-Fritsch scheme for deep convection is now being tested together with the so-called MixPhas Tremblay scheme for grid-scale condensation. Different shallow and intermediate convective schemes such as a modified version of the Kain-Fritsch scheme, the Betts-Miller scheme, and a new scheme from von Saltzen and MacFarlane are currently examined. The boundary-layer turbulence scheme has also been modified in order to include the effect of condensation on the vertical diffusion. Comparison between results from this new configuration and from the current 100-km operational model will be shown at the conference. In particular, we are interested in the potential increase of mesoscale predictability of mid-latitude weather systems that could result from the use of the proposed configuration.