University of Isfahan Journal of Applied Climatology 2476- 4264 3 1 2016 06 21 A Study of Frost Season Variability in Hamadan Province A Study of Frost Season Variability in Hamadan Province 41 56 23220 10.22108/jac.2018.79417.0 FA Zohreh Maryanaji Assistant Professor, Department of Geography, Department of Geology, University of Seyyed Jamaloddin Asad Abadi, Hamadan, Iran Ali Baratian PhD in Climatology, Geosciences Research Center, University of Isfahan, Isfahan, Iran Journal Article 2016 04 24 Climate change is one of the current problems of human society and is a threat to the earth. The increase in the temperature of the earth caused extensive changes in earth’s climate and also leaded to changes in the time and place of frost season. This study attempts to identify the changes in frost season in Hamadan province. For this purpose, the dates of the first frost in autumn and the last frost in spring was extracted from daily minimum temperature data in Hamadan province, and thus the frost season was determined and the linear trend and their possible changes during a 20-year period of 1993-2012 were analyzed. For this purpose, the observations were split into two decades. The results of this study show that in both decades, the frost season is about to begin in the late of autumn. Thus, the frost season is short and squeezed. This shift in the first decade was more intense than the second decade, which means that in recent years, the frost season has moved at a relatively slow pace towards mid-winter. In order to classify, frost seasonal variability was interpolated and the cluster analysis was done based on the ‘Euclidean mean distance’ and ‘Ward’ integrated method. Based on this, Hamadan province was classified into four regions in terms of frost season variability. The first and second regions, which are northern parts of the province, have a cold climate with the most changes, the third region has a shortened autumn and spring frost and compression of the frosty season to the winter. The 4th region has no significant change. The results of this research can be used to predict the occurrence of frost and its application in agricultural planning. Climate change is one of the current problems of human society and is a threat to the earth. The increase in the temperature of the earth caused extensive changes in earth’s climate and also leaded to changes in the time and place of frost season. This study attempts to identify the changes in frost season in Hamadan province. For this purpose, the dates of the first frost in autumn and the last frost in spring was extracted from daily minimum temperature data in Hamadan province, and thus the frost season was determined and the linear trend and their possible changes during a 20-year period of 1993-2012 were analyzed. For this purpose, the observations were split into two decades. The results of this study show that in both decades, the frost season is about to begin in the late of autumn. Thus, the frost season is short and squeezed. This shift in the first decade was more intense than the second decade, which means that in recent years, the frost season has moved at a relatively slow pace towards mid-winter. In order to classify, frost seasonal variability was interpolated and the cluster analysis was done based on the ‘Euclidean mean distance’ and ‘Ward’ integrated method. Based on this, Hamadan province was classified into four regions in terms of frost season variability. The first and second regions, which are northern parts of the province, have a cold climate with the most changes, the third region has a shortened autumn and spring frost and compression of the frosty season to the winter. The 4th region has no significant change. The results of this research can be used to predict the occurrence of frost and its application in agricultural planning. https://jac.ui.ac.ir/article_23220_bde82c09a500b9c56cda95fa25043ff4.pdf