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Improving a global model from the boundary layer: total turbulent energy and the neutral limit Prandtl number

Pithan, F., Angevine, W. and Mauritsen, T. (2015) Improving a global model from the boundary layer: total turbulent energy and the neutral limit Prandtl number. Journal of Advances in Modeling Earth Systems, 7 (2). pp. 791-805. ISSN 1942-2466

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To link to this item DOI: 10.1002/2014MS000382

Abstract/Summary

Model intercomparisons have identified important deficits in the representation of the stable boundary layer by turbulence parametrizations used in current weather and climate models. However, detrimental impacts of more realistic schemes on the large-scale flow have hindered progress in this area. Here we implement a total turbulent energy scheme into the climate model ECHAM6. The total turbulent energy scheme considers the effects of Earth’s rotation and static stability on the turbulence length scale. In contrast to the previously used turbulence scheme, the TTE scheme also implicitly represents entrainment flux in a dry convective boundary layer. Reducing the previously exaggerated surface drag in stable boundary layers indeed causes an increase in southern hemispheric zonal winds and large-scale pressure gradients beyond observed values. These biases can be largely removed by increasing the parametrized orographic drag. Reducing the neutral limit turbulent Prandtl number warms and moistens low-latitude boundary layers and acts to reduce longstanding radiation biases in the stratocumulus regions, the Southern Ocean and the equatorial cold tongue that are common to many climate models.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:43568
Publisher:American Geophysical Union

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