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IVES 9 IVES Conference Series 9 The sea breeze: a significant climatic factor for viticultural zoning in coastal wine growing areas

The sea breeze: a significant climatic factor for viticultural zoning in coastal wine growing areas

Abstract

La brise de mer est un facteur climatique important pour le zonage viticole des régions viticoles côtières car l’accélération du vent qui lui est associée l’après midi ainsi que l’augmentation de l’humidité relative et la réduction de la température concomitantes sont significatives pour le fonctionnement de la vigne et, par conséquent, la qualité du raisin et du vin. Le vent, l’humidité relative et la température sont étudiés à partir de données de surface issues de stations météorologiques automatiques situées dans le vignoble au sud ouest de la région du Cap en Afrique du Sud et de simulations numériques sur l’espace étudié afin, d’évaluer le degré de pénétration de la brise de mer et la “limite” de son influence. Les simulations ont été réalisées avec le Regional Atmospheric Modelling System (RAMS) pour trois conditions synoptiques au cours de la période de maturation: un flux à grande échelle de sud, chaud (3/02/2000), un flux de nord très chaud et sec (18/02/2000) et un flux de nord­-ouest frais et humide (19/02/2000). Les résultats des simulations numériques avec une résolution de 1 km montrent que plus les températures sont élevées, plus la baisse des températures générée par la brise de mer est importante. La brise de mer venant de l’Atlantique (Table Bay) le 18/02/2000 a généré une baisse maximale des températures de 6 °C tandis que cette de la False Bay le 3/02/2000 une baisse maximale de 2 °C dans la région viticole de Stellenbosch. Une baisse maximale de 1 °C seulement a été enregistrée lors d’un jour nuageux (19/02/2000).

The sea breeze is an important climatic factor for viticultural zoning in coastal wine producing areas as the associated increase in wind velocity in the afternoon and concomitant increase in relative humidity and reduction in temperature is of significance for vine functioning and, therefore, grape and wine quality. Wind, relative humidity and temperature were studied with the aid of surface data from automatic weather stations in the South Western Cape wine growing area of South Africa as well as numerical simulations over the study domain in order to ascertain the degree of penetration of the sea breeze and to assess the “limit” of its influence. Simulations were performed using the Regional Atmospheric Modelling System (RAMS) for three synoptic conditions during the grape maturation period: a southerly large-scale flow associated with warm temperature (3/02/2000), a northerly large­scale flow associated with hot and dry conditions (18/02/2000) and north-westerly large-scale flow associated with cool and humid conditions (19/02/2000). Results of the numerical simulations performed at a 1-km resolution showed that the warmer the temperature, the greater the temperature decrease induced by the sea breeze. The sea breeze originating from the Atlantic (Table Bay) on 18/02/2000 generated a maximum temperature decrease of
6 °C, while that originating from False Bay on 3/02/2000 generated a maximum temperature decrease of 2 °C in the Stellenbosçh wine producing area. A maximum temperature decrease of only 1 °C was recorded on an overcast day (19/02/2000).

DOI:

Publication date: February 15, 2022

Issue: Terroir 2002

Type: Article

Authors

V. BONNARDOT

ARC Institute for Soil, Climate and Water, Private Bag X5026, 7599 Stellenbosch, South Africa

Contact the author

Keywords

Atmospheric modelling, sea breeze, wine-producing area, South Africa, ripening period

Modélisation atmosphérique, brise de mer, région viticole, Afrique du Sud, période de maturation

Tags

IVES Conference Series | Terroir 2002

Citation

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