determination of freezing and thaw cycles and mapping of susceptible area in khorasan razavi province by using gis

abstract consistent decreasing and increasing of temperature in the short-term period that is called freezing and thaw cycles is one of the important factors of damage to crop productions. in this research as to determine freezing and thaw cycles in the khorasan razavi province, the data of daily minimum and maximum temperatures of 9 synoptic stations was used over 20 statistic years (1989-2008). also 6 distinct range of temperatures including: the minimum temperatures lesser and equal whit -2 and the maximum temperatures greater and equal whit 2 (a), the minimum temperatures lesser and equal whit -3 and the maximum temperatures greater and equal whit 3 (b), the minimum temperatures lesser and equal whit -5 and the maximum temperatures greater and equal whit 5 (c), the minimum temperatures equal whit -2 and the maximum temperatures greater than 2 (d), the minimum temperatures equal whit -3 and the maximum temperatures greater than 3 (e) and the minimum temperatures equal whit -5 and the maximum temperatures greater than 5 were presented. after data processing by a computer program into the fortran space, the number of days with this phenomenon for each station was determinated as monthly, seasonal and annual and then the mapping plans of susceptible areas were prepared. the results show that winter has a higher rate of this phenomenon and autumn and spring are next respectively. also the investigation of mapping plans indicated that in most temperature ranges, the torbat heydariye, nishaboor and ghuchan stations had maximum number of freezing and thaw cycles in khorasan razavi province. the minimum rate of this phenomenon was in the sarakhs, kashmar and sabzevar stations as well.