Gravity-Wave Drag in the Stable Boundary Layer Over Moderate Terrain
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Two previous studies of vertical stress profiles due to gravity waves in the stable boundary layer have given differing results. The current study uses a high-resolution numerical forecast model to determine the effect of moderate topography on the vertical stress profile due to gravity waves in the stable boundary layer. The results show that while a quadratic stress profile is expected when topography is low compared to the stable boundary-layer height, when topography height is moderate the pressure term in the valleys becomes dominant. This results in a linear effective stress profile below the hill tops with possibly some remnant stress transmitted up into the troposphere.
KeywordsEvening transition Gravity-wave drag Stable boundary layer
We would like to thank members of the Met Research Unit at Cardington for setting up and maintaining the surface-site network and the numerical-forecast group at Exeter for help with the numerical model output archive. Particular thanks are due to Glenn Shutts for advice on gravity waves. The input of three referees is also gratefully acknowledged.
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