THE EFFECT OF SLOPE-ASPECT ON TURBULENT TRANSFER IN AN ALPINE FELLFIELD: NIWOT RIDGE,FRONT RANGE,COLORADO |
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Authors: | Scott A Isard |
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Institution: | Department of Geography , University of Illinois at Urbana-Champaign , Urbana, Illinois 61801 |
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Abstract: | This study investigates the impact of local convergence and divergence of air on turbulent transfer at a mid-latitude alpine fellfield site. Pairs of simultaneous wind and temperature profile measurements on a knoll crest and primary slope (aspect =0, 90, 180, and 270°) are analyzed assuming the logarithmic law. Friction velocity (u*) and roughness length (z0) vary systematically from windward to leeward slopes. General relationships of the form u* = f(u) are derived for conditions of westerly flow with wind speed (u) ranging between 2 and 24 m s-1. Coefficients in the empirical equations for estimating u* at sites on the knoll from wind speed measurements on the crest vary in a consistent manner with respect to local convergence and divergence. Large differences in z0 values between windward and leeward sites correspond with contrasts in surface temperature. |
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