Investigation of Dry Days Occurrence Probability in Golestan Province Using Markove Chain Model

In this research based on 51 synoptic, climatologic and rain gauge stations of Golestan province with at least 20 years length the dry spell with zero and 1 mm threshold have analyzed using Markov chain models.Spatial distribution of precipitation in Golestan is depends on longitude, latitude and specially elevation variables. So that the precipitation increases across north to south while the wet and dry days have changed with. Dry days occurrence probability in Golestan is 0.73 to 0.91 by the mean of 0.83 while it is 0.765 to 0.91 and 0.84 respectively for precipitation less than 1 mm. The range of occurrence probability decreasd when the precipitation threshold increased with occurrence probability growth.The spatial changes of dry days probability is not notable, so with based on the relationship between dry day probability and precipitation rates concluded that increase in precipitation is caused decrease in the dry day toward less precipitation regions. The results of this paper show more intense precipitation in south of province in compare with north parts in a few days. The dry spell is very shorter in the southern part of province in compare to the northern part in similar days.