بررسي تغييرات طول دوره بدون يخبندان وتعداد روزهاي يخبندان در استان هاي آذربايجان غربي و شرقي

Study of Change in the Frost Free Season Length and Number of Frosty Days in the Western and Eastern Azarbaijan Provinces

One of the most important impacts of recent global warming and climate change is increasing the number of frost days and frost free season length. To detect these changes in Azerbaijan provinces, where produce many agricultural products in Iran, 8 meteorological stations with more than 30 years and high quality data were selected in that region. By using the daily minimum temperature, the number of frost days and frost free season length were calculated. The linear trend and their significance, in association with significant changes in decadal means and variances of those parameters were determined by statistical methods. The results show that, the number of frost days has decreased in the most of stations except, Oroomieh and Jolfa. There are no significant changes in decadal mean for Tabriz, Oroomieh, Miyandoab, Sarab and Maragheh stations. Changes in decadal variance for Miyandoab are significant. Increasing trends of the length of frost free season were observed in Oroomieh, Jolfa, Sarab and Ahar. On the contrary, decreasing trend was observed in Tabriz, Maragheh and khoy. Stationary trend was also observed in Miyandoab. Further more no significant changes in decadal means have been experienced. In general, the obtained results are not consistence with the pattern of global changes for number of frost days and frost free season length.