Wednesday, 14 January 2004
CLOUDS AND PRECIPITATION FROM A GLOBAL NWP MODEL
A mesoscale version of the Global Environmental Multiscale (GEM) model, with a uniform resolution of 0.45 degree in longitude and latitude , has been under development in the last two years at the Meteorological Research Branch and the Canadian Meteorological Centre. Apart from the increased horizontal and vertical resolutions (58 levels are used compared to 28 in the current operational configuration), significant changes are proposed to the representation of physical processes. The most important of these changes are the following: the Kain-Fritsch deep convective scheme replaces the Kuo scheme; a so-called Kuo Transient scheme is now being used to represent shallow convective activity; and the mixing length used for the vertical diffusion processes (for boundary-layer turbulence) is now calculated using the Bougeault-Lacarrere technique.
Two series of 120 hour simulations were conducted spanning the winter season of 2001-2002 and the summer season of 2002. These simulations were analyzed with special emphasis on determining the physical realism of the the global-scale distribution and variability of precipitation, humidity, cloud cover, cloud water content as well as on top of atmosphere and surface radiative fluxes. This is accomplshed by comparing the model output to observations provided by GPCP,ARM,CERES,CAVE surface network and SSMI and TRMM satellites. At the conference we will briefly describe this new version of the canadian GEM NWP model as well as present the results of the analysis discussed above.