Detection and analysis of winter precipitation over south east of Iran

In this study, the data of winter precipitation in four synoptic meteorological stations Zabol, Zahedan, Iranshahr and Chabahar in south east of Iran were investigated to detect wet and dry winters of this region. The gamma distribution function is fitted on the winter precipitation data and then based on the applied relation on the curve, the precipitation upper 90% and lower 10% are estimated in each station. By choosing two very wet winters and two very dry winters for the southern and northern half of the province, anomalies of the mean sea level pressure and height of 500 hPa were investigated. The investigation of winter precipitation data showed that, winter precipitation varies between 50 to 59 percent of total precipitation in different stations of the province. The results were detected a few very dry winters and a few very wet winters in four stations of Sistan and Balochestan. In the two very dry winters, due to the development of the westward the cold high pressure and development of the eastward the Azores high pressure, the frequency of the creation and development of low pressure has decreased and their route has changed from Iran. In very wet winters, the upper trough has deep and the frequency of low pressure and their route from Iran has increased. During these winters, the activity of the Red Sea trough inverse has increased, which has led to heavy precipitation in the southern regions of the Iran and stations in Sistan and Balochistan.