Analysis of changes in viticultural climatic indices in northwestern and western Iran




Climate and climatic variables are very important factors in grape growth. Usually, temperature variables (maximum, average and minimum), as well as pre-
cipitation variables (annual, monthly and daily), are used to determine the regional climate and to study the type and amount of climate change. Most of the viticultural climatic indices presented by researchers have been using the above variables. Northwestern and western regions of Iran are considered as the most important areas of grape cultivation with different climatic conditions in different parts that have led to the cultivation of grape cultivars. In this study, five temperature indices (Huglin, latitude-temperature, night cooling, temperature variability and Winkler) and two precipitation indices were investigated based on De Martonne and hydrothermal drought indices. Then, they were analyzed by Mann-Kendall method and Sen's slope estimator index. The studies showed significant positive trends in Huglin, Winkler, night cooling and latitude-temperature indices, while the temperature variability index is significant only in a few stations. On the other hand, the indices related to drought and hydrothermal show no trend. However, some southern stations in the region showed a different trend in some indices. As a result, the trend of changes in temperature indices can lead to the expansion of cultivation of grape cultivars in the coming years, although the limitation of water resources will be a negative factor.