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Lake Gray


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Fort Smith, Unorganized AB
Canada

Modelling topographic effects on winds in the Alberta oil sands area


Author(s): Danard, M., & Gray M.

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.

Relict grassland in northern Saskatchewan: A phytogeographic study in the Clearwater River Valley


Author(s): Johnson, R. H.

Year: 1989

Abstract:
The main purpose of this research was to characterize the vegetation of the open slopes along the lower Saskatchewan reach of the Clearwater River. Examination of the species that constitute a representative site and the environmental conditions within which they exist was essential to the prediction of vegetation status and continued site occupation. An hypothesis was put forward on the origin of these communities and various methods to measure environmental parameters were used to determine the present site conditions. Many plants of the community were found to be displaced in Saskatchewan flora range and outside their normal climatic region. Most notable species are Anemone cylindrica A. Gray, Artemisia frigida Willd., Aster conspicuus Lindl., A. laevis L., Penstemon gracilis Nutt. and Stipa curtiseta (Hitchc.) Barkworth. Near the steppe study site, Abiesbalsamea (L.) Mill. exists as an isolated population in well protected spring-sapping zones. Calamagrostis purpurascens R. Br., a northern resident found previously as far south as the Cluff Lake area, represents a southern range extension. The data collected suggest recent advancement of footslope overstory but that maximum upslope movement may have been reached. The grassland species present are explained as being a relict community of previously widespread steppe origin.