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Changes in atmospheric circulation and temperature trends in major vineyard regions of New Zealand

Authors


Correspondence to: A. Sturman, Department of Geography, Centre for Atmospheric Research, University of Canterbury, Private Bag 4800, Christchurch, New Zealand. E-mail: andrew.sturman@canterbury.ac.nz

ABSTRACT

This paper contributes to knowledge of the impact of global warming on viticulture, using major vineyard regions of New Zealand as a case study to illustrate regional disparities in climate change impacts resulting from downscale effects of larger scale atmospheric circulation. Recent trends in air temperature in New Zealand vineyard areas are investigated. Trends since 1941 in Marlborough show an increase in temperature range, with both rising maximum temperatures and declining minimum temperatures, but no change in the annual mean. More hot days and frosts are of concern to viticulturalists, and this trend not only differs from other major vineyard areas, but also occurs at other sites in eastern parts of the country. The relationship between changes in atmospheric circulation over New Zealand and observed trends in temperature and frost occurrence at Blenheim is investigated using the Kidson weather type classification for the period 1958–2010 and the Trenberth M1 index. The increased temperature range is expected to be associated with more frequent clear skies along the east coast of the country, resulting from changes in weather patterns (more frequent anticyclones, fewer low-pressure systems, increased zonal and southerly flow). These changes in weather patterns are shown to be closely linked to larger scale changes in atmospheric circulation via the Southern Annular Mode (SAM) and Southern Oscillation. The results show that significant regional variations in the impact of global warming can occur over areas of complex terrain such as New Zealand. Observed differences in local temperature and frost trends can be caused by the interaction of changing weather systems with mountainous terrain. These changing weather systems themselves are seen to be the result of major shifts in the larger scale atmospheric circulation. These results are important for assessing possible impacts on viticulture and in developing adaptation strategies for agriculture in response to predicted future climates.

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