MODELING THE SPATIAL VARIATIONS OF WIND-SPEED AND DIRECTION ON ROUNDTOP MOUNTAIN, QUEBEC

A computer model for windflow in complex terrain (MS-Micro/3) is applied to the Roundtop Mountain complex (maximum elevation 970 m above sea level) in southern Quebec. A brief description of the model is given, together with a description of the terrain and the particulars of the present application. The model is applied to near steady-state conditions for three different undisturbed-flow wind directions. Variations in wind speed and direction, as computed by the model and depicted as horizontal cross-sections, two-dimensional isopleth plots and vector plots, are related to topographic variations. Model results for Roundtop Mountain are compared with observations collected, as part of the Chemistry of High Elevation Fog (CHEF) project, over nine periods of near-steady winds. Within the limits of uncertainty in the observations and associated model input values, model results of CHEF ridge-to-valley site wind-speed ratios agreed with observed ratios in six of the nine periods investigated. Spatial variations in wind speed and direction calculated from the model follow terrain features, with highest wind speeds on ridges and lowest in valleys.