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IVES 9 IVES Conference Series 9 Weather classification over the Western Cape (February, 1996 – 2000) and viticultural implications in the Stellenbosch wine district

Weather classification over the Western Cape (February, 1996 – 2000) and viticultural implications in the Stellenbosch wine district

Abstract

[English version below]

Une étude préliminaire des situations météorologiques journalières a été réalisée pour l’Afrique du Sud et pour les mois de février (période de maturation des raisins dans la Province occidentale du Cap), à l’image de la classification synoptique réalisée aux latitudes tempérées en France (Jones & Davis, 2000), afin d’étudier les relations entre le climat et la viticulture à des latitudes plus basses. Les bulletins météorologiques journaliers du South African Weather Service (SAWS) et les données de surface observées par le SAWS à l’aéroport international du Cap ont été utilisés. Les situations météorologiques synoptiques ont été classées en quatre groupes principaux: la crête de haute pression atlantique sur l’ouest de l’Afrique du Sud, le passage d’une dépression atlantique sur la Province Occidentale du Cap, la prédominance de la dépression ouest, et la crête de haute pression de l’Océan Indien sur l’est du pays. Parmi ces quatre groupes, deux prédominent sur la Province Occidentale du Cap: la crête de haute pression atlantique et de la dépression ouest. Pour les cinq saisons étudiées (1996-2000), la haute pression atlantique représente 48% des cas et la dépression ouest 34%. La fréquence de la haute pression atlantique varie entre 61% (1997 et 1998) et 36% (1999). Comparant ces fréquences avec des recherches antérieures sur l’influence du millésisme et du mésoclimat sur les arômes des vins (Carey et al., 2003), il a été trouvé par example que des conditions plus chaudes en 1998 (résultant du temps ensoleillé associé à la dépression ouest centrée sur la Province du Cap) avaient abouti à la prédominance d’un arôme de fruits tropicaux dans les vins de Sauvignon blanc, et d’un arôme de fruits d’arbre dans les vins de Chardonnay. Il semble que le temps associé aux conditions synoptiques prédominantes aient des implications significatives sur le style de vin. La connaissance de ces conditions et de leur variation au cours de la période végétative aidera ainsi aux études de modélisation climatique avec application pour la viticulture.

A preliminary study of the daily weather situations was performed for February in South Africa (ripening period of the grapes in the Western Cape), similar to the synoptic classification realized for the temperate latitudes in France (Jones & Davis, 2000), in order to focus the study of the relationships between climate and viticulture at lower latitudes. Daily weather bulletins of the South African Weather Service (SAWS) and surface data observed at Cape Town International Airport by the SAWS were used. The synoptic weather situations were classified in four main patterns, namely: the ridging of the Atlantic Ocean High over the western parts of South Africa, the passing of a cold front over the Western Cape, the dominance of the west coast trough, and the ridging of the Indian Ocean High over the eastern parts of South Africa. Of these four groups, two are predominantly occurring over the Western Cape, namely the ridging of the Atlantic Ocean High and the west coast trough. The Atlantic Ocean High occurs on 48% of the days in February over the five seasons (1996-2000) used for the classifications, whilst the trough occurs on 34% of the days. The occurrence of the Atlantic Ocean High varies between 61% (1997 and 1998) and 36% (1999). Comparing these occurrences with previous research on the influence of vintage and meso-climate on wine aroma, it was found, for instance, that warmer conditions (the result of sunny skies associated with the west coast trough situated over the Western Cape) in 1999 resulted in predominant tropical fruit aromas in the Sauvignon blanc wines, and tree fruit aromas in Chardonnay wines. It appears as if the weather associated with dominant synoptic conditions holds significant implications for wine style. Knowledge of these conditions and their variation over the entire season will then help in climatic modelling studies for application to viticulture.

DOI:

Publication date: January 12, 2022

Issue: Terroir 2004

Type: Article

Authors

C.B. du Preez (1), V.M.F. Bonnardot (1) and V.A. Carey (2)

1) ARC-Institute for Soil, Climate and Water, Private Bag X5026, Stellenbosch, 7599, South Africa
2) Department of Viticulture and Enology, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa

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IVES Conference Series | Terroir 2004

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