Using historical weather data and a novel season temperature index to classify winegrape growing zones in Australia

Abstract

• Australian wine regions can be classified into different climatic categories; • Drier growing seasons were observed for many wine regions from 1911 to 2017; • Warmer growing season/night-time temperature were observed for most wine regions; • The climatic changes in different wine regions differed over historical time periods; • Many wine regions became less suitable to grow temperate grape varieties. Viticultural production and wine quality are profoundly affected by climate. Characterising winegrape-growing regions based on climatic variables provides scientific guidance for the wine industry in vineyard site and winegrape cultivar selection. This research used a modified multicriteria climatic classification system based on three representative indices, Huglin index, cool night index and growing season relative soil moisture to classify 63 southeastern Australian winegrape-growing regions into different climatic categories, within different historical time periods from 1911 to 2017. The pattern of changes in climatic classification over these time-periods were identified for each region and illustrated in the principal component analysis (PCA) plot. A second classification system based on growing season average temperature index was further used to identify the temperature variations among regions. Based on this, a novel grapevine suitability index was generated to indicate the suitability of growing key commercial winegrape varieties in a specific winegrape-growing region. Clear changes in regional climate across the three historical time periods were observed in majority of the studied regions with clear differences between regions. Warmer growing season, warmer night-time temperature and drier growing season were the most frequently observed trends. GST analysis showed that median temperature increased for majority of winegrape-growing regions with more extreme hot climatic conditions appearing in recent years. Some winegrape-growing regions have become less suitable for temperate winegrape varieties and may need to move to more heat tolerant varieties, while some cold regions became more suitable for winegrape production. Climatic variations were observed among non-official geographic indications (GIs), which provided the scientific basis for the possible separation of these regions. This study will assist the wine industry to better understand the climatic variations between viticulture regions, and provide guidance for the selection of the most suitable winegrape varieties within each region and the selection of regions to grow particular varieties.