Articles | Volume 13
https://doi.org/10.5194/asr-13-107-2016
https://doi.org/10.5194/asr-13-107-2016
08 Jul 2016
 | 08 Jul 2016

Influence of sea surface roughness length parameterization on Mistral and Tramontane simulations

Anika Obermann, Benedikt Edelmann, and Bodo Ahrens

Abstract. The Mistral and Tramontane are mesoscale winds in southern France and above the Western Mediterranean Sea. They are phenomena well suited for studying channeling effects as well as atmosphere–land/ocean processes. This sensitivity study deals with the influence of the sea surface roughness length parameterizations on simulated Mistral and Tramontane wind speed and wind direction. Several simulations with the regional climate model COSMO-CLM were performed for the year 2005 with varying values for the Charnock parameter α. Above the western Mediterranean area, the simulated wind speed and wind direction pattern on Mistral days changes depending on the parameterization used. Higher values of α lead to lower simulated wind speeds. In areas, where the simulated wind speed does not change much, a counterclockwise rotation of the simulated wind direction is observed.

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Short summary
Simulated surface winds in atmospheric models depend, among others, on the parameterization of the sea surface roughness. Three parameterizations (variation of Charnock parameter) were tested in the western Mediterranean area during Mistral events with the regional climate model COSMO-CLM. While the whole sea level pressure pattern did not change much, a larger Charnock parameter led to lower wind speeds and a rotation of the wind direction.