Editorial Type:
Article
Article Type:
Research Article

Mesoscale Atmospheric Modeling Using a High Horizontal Grid Resolution over a Complex Coastal Terrain and a Wine Region of South Africa

V. Bonnardot Institute for Soil, Climate and Water of the Agricultural Research Council, Pretoria, South Africa

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S. Cautenet Laboratoire de Météorologie Physique, UMR 6016-CNRS, Blaise Pascal University, Aubiere, France

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Print Publication:
01 Feb 2009
DOI:
https://doi.org/10.1175/2008JAMC1710.1
Page(s):
330–348
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Abstract

The Regional Atmospheric Modeling System (RAMS) was used to assess local air circulation patterns over the wine-producing Stellenbosch region of South Africa. Numerical simulations using four nested grids (25, 5, and 1 km, and 200 m of horizontal resolution) were performed for each day of February 2000 (during the grape-ripening period) over southern Western Cape Province. Modeled hourly data were extracted from the analysis files and used to produce mean hourly fields (temperature, relative humidity, wind speed, and radiation). Three runs with increasing horizontal resolutions for the finer grid were performed (run 1 with two nested grids of 25 and 5 km; run 2 with three nested grids of 25, 5, and 1 km; run 3 with four nested grids of 25, 5, and 1 km, and 200 m). For each event, the simulations of 1-km and 200-m resolution were superior to the 5-km-resolution simulation, especially in reproducing the local air circulations (sea and slopes breezes) because of a better representation of the local terrain (topography and vegetation cover). The use of a high-resolution grid (200 m) may be of greater value in the identification of potential terrain for viticulture.

* Current affiliation: Bureau d’Études et de Recherches en Climatologie Appliquée à la Vigne, Cranves-Sales, France.

Corresponding author address: Prof. Sylvie Cautenet, Laboratoire de Météorologie Physique, Blaise Pascal University, 24, Av. des Landais, Aubiere 63170, France. Email: s.cautenet@opgc.univ-bpclermont.fr

Abstract

The Regional Atmospheric Modeling System (RAMS) was used to assess local air circulation patterns over the wine-producing Stellenbosch region of South Africa. Numerical simulations using four nested grids (25, 5, and 1 km, and 200 m of horizontal resolution) were performed for each day of February 2000 (during the grape-ripening period) over southern Western Cape Province. Modeled hourly data were extracted from the analysis files and used to produce mean hourly fields (temperature, relative humidity, wind speed, and radiation). Three runs with increasing horizontal resolutions for the finer grid were performed (run 1 with two nested grids of 25 and 5 km; run 2 with three nested grids of 25, 5, and 1 km; run 3 with four nested grids of 25, 5, and 1 km, and 200 m). For each event, the simulations of 1-km and 200-m resolution were superior to the 5-km-resolution simulation, especially in reproducing the local air circulations (sea and slopes breezes) because of a better representation of the local terrain (topography and vegetation cover). The use of a high-resolution grid (200 m) may be of greater value in the identification of potential terrain for viticulture.

* Current affiliation: Bureau d’Études et de Recherches en Climatologie Appliquée à la Vigne, Cranves-Sales, France.

Corresponding author address: Prof. Sylvie Cautenet, Laboratoire de Météorologie Physique, Blaise Pascal University, 24, Av. des Landais, Aubiere 63170, France. Email: s.cautenet@opgc.univ-bpclermont.fr

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Journal of Applied Meteorology and Climatology

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