Some Aspects of the Structure of Convective Planetary Boundary Layers

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  • 1 Air Force Cambridge Research Laboratories, Bedford, Moss. 01730
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Abstract

It is shown that although Coriolis forces cause large production rates of stress in a convective planetary boundary layer, there is a control mechanism, involving mean wind shear which prevents stress levels from becoming large. Higher-order-closure model calculations are presented which show that the stress profiles are essentially linear, regardless of wind direction, providing the geostrophic wind shear vanishes and the wind speed jump across the capping inversion is negligible. It is shown that it will he very difficult to verify these predicted stress profiles experimentally because of averaging time problems. A simple two-layer model is developed which leads to geostrophic drag and heat transfer expressions in fairly good agreement with Wangara data.

Abstract

It is shown that although Coriolis forces cause large production rates of stress in a convective planetary boundary layer, there is a control mechanism, involving mean wind shear which prevents stress levels from becoming large. Higher-order-closure model calculations are presented which show that the stress profiles are essentially linear, regardless of wind direction, providing the geostrophic wind shear vanishes and the wind speed jump across the capping inversion is negligible. It is shown that it will he very difficult to verify these predicted stress profiles experimentally because of averaging time problems. A simple two-layer model is developed which leads to geostrophic drag and heat transfer expressions in fairly good agreement with Wangara data.

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