Statistical analysis of the frequency and stability of the frost days in southern Khorasan Province, using Markov Chain Model

Cold and frost waves are are among the most important natural phenomena, occuring in the cold period of the year. The reason why the frost phenomenon has been considered is it's feedbacks on the nature and human life, which sometimes has been associated with negative severe tension and sometimes positive feedbacks, particularly in agriculture and gardening. This study has tried to analysis of daily, as monthly and seasonal, frosts of Southern Khorasan province. To do this, the minimum daily temperature of synoptic stations of Southern Khorasan province were used for a 27 years period (1988-2014). And to investigate the probability and frequency of the frost days, Markov chain model was used. Results illustrated that Ghaen city in the north, and Birjand city in center of Southern Khorasan province, had the maximum occurrence and frequency of the frost days, respectively. Among the stations, Nehbandan city has experienced the minimum probability of frost days. Two-days continuities in all stations, revealed the minimum return period, indicating the less continuity of frost days in Southern Khorasan province.. All the analyzed stations in the studied area, except for Nehbandan, which generally hasn't experienced any frost day, are characterized by Markov chain, first class. In other words, any occurrence of frost days, depend on climate conditions of past days. The beginning of autumn frost days of Southern Khorasan province, is in November, known as the first autumn frost; and the beginning of winter frost is concentrated in January. The maximum frosty cycle in October have been occurred in Ghaen station about 0.058, and in November in Ferdos and Boshrooye stations about 0.05 and 0.043, respectively. Results confirmed the obvious role of high and mountain regions in the frequency and continuity of frost days in the province.