Year: 1982
Abstract:
Two versions of the mesoscale, one-level, primitive equations wind model of Danard (1977) have been adapted to northeastern Alberta. The model starts from a surface wind obtained from a balance between large-scale pressure gradient, Coriolis, and frictional forces. The surface temperatures and pressures are changed by adiabatic flow over varying terrain and non-adiabatic heating. The changes in horizontal pressure gradient force then modify the surface winds to account for small-scale topographic effects. This is referred to as dynamical adjustment. In one version of the model, the Stoney Mountain model, geestrophic winds are obtained from Atmospheric Environment Service (AES) sea-level and 850mb charts. In the other application, the Mildred Lake model, the thermal and momentum boundary layers are estimated directly from high-resolution vertical profiles of temperatures and winds provided by minisondes. Geostrophic winds and isobaric temperature gradients are obtained from observed minisonde winds above the momentum boundary layer. The Stoney Mountain model is applied to ten cases and the Mildred Lake version to six. The cases were chosen because good data were available and because they provided variety in wind direction, season, and synoptic conditions. In the Stoney Mountain model, 50% of the time, the difference between reported and computed speeds is less than 2.8 km/h in magnitude. The fiftieth percentile for angle difference is only 90 . For the Mildred Lake version, fiftieth percentiles for the magnitude of the speed and angle differences are 2. 7 km/h and 190, respectiveIy.
