Analyzing of trend changes in the frost threshold (Case Study: Northwest of Iran)

Frost is a climatic phenomenon in which water is at or below freezing point. A frost day refers to a day when the temperature goes down under zero Celsius degree throughout the night. Frost has important impacts on various aspects of human life, especially on agriculture and food productions. In the current study, the non-parametric (Mann-Kendall), parametric (Pearson correlation coefficient) and Innovative Trend Analysis (Sen) procedures were used to evaluate the effects of changing the trend of frost threshold in Northwest area of Iran. Based on Mann-Kendall and Pearson tests, there was a negative trend at Ardebil, Parsabad, Makoo, Maragheh and Mahabad stations, however, this effect was significant only at Ardebil station (p