Topographic influence on surface winds

Abstract

Using data collected during 1975–1976 from a meteorological network operating in the vicinity of the Columbia Generating Site approximately 8 km south of Portage, Wis., the influence of the Baraboo Hills on the surface wind field is determined. Half-hour means of wind speed and direction measured at 9 m at three sites were used to compute divergence and vorticity using Bellamy's method. The data were grouped into 18 sectors each 20 deg wide and averages computed for each quantity. Results indicate that for wind directions perpendicular to the eastern edge of the Baraboo Hills, the surface (9m) wind field is significantly perturbed up to 4 km from the bluffs. The largest convergence of 2.1 × 10⁻⁴ s⁻¹ occurs with 160 deg wind direction and the largest divergence of 1.2 × 10⁻⁴ s⁻¹ with 290 deg wind direction. The maximum anticyclonic vorticity was 1.6 × 10⁻⁴ s⁻¹ at 210 deg and the maximum cyclonic vorticity was 1.6 × 10⁻⁴ s⁻¹ at 330 deg.