Analysis of Rainy Days Occurrence Probability Using Markov Chain Model for City of Urmia Iran

At present paper the frequency and the spell of rainy days in Urmia have been analyzed by using probability rules and Markov chain technique. The 48-year rain data (1961-2008) for Urmia synoptic station is used. The frequency matrix is formed and the probability matrix of rainy–dry days is created. Accordingly based on maximum likelihood method, recurrence interval is estimated on the basis of succeeding power on probability matrix. Rainy and dry days have 5 and 1 year return period. Rainfall occurrence probability on each day was about 0.2057 and dry occurrence probability was 0.7943. Continuous return period on rainy days with continuity of 1 to 5 day has been calculated. According to the calculations it was clear that maximum occurrence probability on rainy days was for spring especially (in April) whit 2 or 3 rainy day return period probability being was equal to 4.4 and 13 days respectively.