Valérie Bonnardot

Suitability of Some Climatic Parameters for Grapevine Cultivation in South Africa, with Focus on Key Physiological Processes

To optimise the functioning of the grapevine in a specific environment and to improve grape and wine quality, suitability of climatic parameters for key grapevine physiological processes needs to be assessed at fine scales. This paper presents methodology using hourly weather data in three wine producing regions of South Africa (Coastal Region – Stellenbosch district; Breede River Valley – Robertson district; Central Orange River Region – Upington district) during the pre- (November to December) and post-veraison (January to February) periods. Durations inside and outside an optimum climatic range and of extreme climatic conditions were calculated over a 5-year period (1999/2000 to 2003/2004) to quantify a climatic profile related to grapevine physiological requirements. Climatic requirements for optimum photosynthetic activity were defined as follows: temperature 25°C to 30°C, windspeed 35°C, >4m/s, 80%. A coefficient was assigned to each climatic parameter according to an assumed importance level for physiological processes. Optimum temperature requirements for other physiological parameters were also investigated. A diurnal minimum/maximum temperature range of 25°C to 30°C was used for sugar content and organic acid levels and a maximum night/day temperature range of 15°C/25°C for colour and flavour. Light intensity was accepted as being sufficient. Stations were classified according to their potential for meeting the climatic requirements of each physiological parameter. Marked variation in climatic profiles and available time for optimal physiological functioning occurred between regions. All factors considered, the climatic profile of the Coastal Region (Stellenbosch district) seemed to best satisfy the climatic requirements of the physiological parameters studied.

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

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 ...

Climate change and the future of South Africa's wine industry

Purpose – The purpose of this article is to attempt to synthesise the lessons from at least four different ways of looking at the South Africa wine industry: economics, climatology, viticulture, and the sociology of work.Design/methodology/approach – The economic performance of South Africas wine industry since democratisation in the early 1990s is reviewed, as is the effect of climate change on the industry. This is followed by an assessment of possible strategies for building international competitiveness whilst simultaneously coping with the effects of climate change.Findings – While industry systems should allow the marketing of speciality wines (e.g. from a single vineyard, from a single estate), this is not a viable strategy for most wine producers. Furthermore, climate change will lead to volatility in the characteristics that identify different terroirs.Practical implications – Industry strategies should rather focus on the benefits of diversity, but with a range of adaptations that will also res...

Vineyard identification and characterization based on texture analysis in the Helderberg Basin (South Africa)

In this paper, a methodology for the spatial identification and characterization of vineyards using texture analysis is proposed to meet the need of ongoing and further viticultural “terroir” studies. The proposed method is based on the maximization of a criteria that deals with the coefficients enclosed in the different bands of a wavelet decomposition of the original image. More precisely, we search for the orientation that best concentrates the energy of the coefficients in a single direction. For each texture pattern, a degree of anisotropy and the angle of the main orientation is extracted. The methodology is validated on aerial-photographs in the Helderberg Basin (South Africa). The degree of anisotropy is a reliable information able to discriminate vineyards to other land-uses. Moreover, the row orientation turns out to be a relevant information for all applications related to mesoscale atmospheric modeling in vineyard areas.