INVESTIGATION OF METEOROLOGICAL DROUGHTS IN THE SISTAN AND BALOUCHESTAN PROVINCE, USING THE STANDARDIZED PRECIPITATION INDEX AND MARKOV CHAIN MODEL

Drought is an insidious environmental phenomenon which is more pronounced in arid and semi arid regions. Central, eastern, and southern regions of Iran are characterized as arid and semi arid climate. Precipitation variability in the Sistan and Balouchestan Province is very high. This is due to remoteness from Mediterranean cyclonic trajectory and the predominance of a subtropical high pressure system. Accordingly, the Sistan and Balouchestan is more prone to drought than other provinces in Iran. In this paper, the probability of drought occurrence and extent in this province is investigated applying lag-1 Markov chain on SPI time series in 3and 6-month time scales. The results showed that the probability of drought persistence, based on 6-month SPI time series, is higher than 70 percent in central portion of the province and decreases to 50 percent moving east. Considering the drought equilibrium probability, the results also indicated that the central district of the province are affected by drought events 30% of the time and therefore is more vulnerable to drought conditions compared to other regions in the province.