Maximum daily precipitation in Iran (1979-2018)

This article deals with daily precipitation intensities. The maximum daily precipitation values were calculated for return periods of 10, 20, 50, and 100 years using the daily precipitation levels recorded at 42 meteorological stations between 1979 and 2018. Three extreme value probability distribution adjustments were used to do this: Weibull, Generalized Extreme Value, and Gumbel. While all fit the annual maximum daily rainfall series well, Weibull produces lower values than the other two distribution methods. The results show considerable differences between the Caspian fringe in the north, with values reaching 300 mm in Ramsar for a return period of 50 years, and some of the more arid eastern areas of the country, where values were less than 40 mm. An area near the Strait of Hormuz in the south was also identified as having high values. The maximum daily precipitation correlates positively with the annual total and negatively with altitude.