ALBERT

Description: Evaluating the susceptibility of regional climates to climate change gives a pattern to realistically analyze the probable future climate changes. This paper investigates human influence on variations in precipitation extremes in Iran by evaluating precipitation data provided from 286 rain-gage stations during 1967-2010 and general circulation simulation results of CanESM2 model. This investigation was based on six forcing factors including natural external (volcanic aerosol, solar radiation), anthropogenic and a combination of them, Green House Gases (GHGs), change of land use, and anthropogenic aerosols. Seven precipitation indices namely Rx1day (Annual maximum 1-day precipitation), Rx5day (Annual maximum 5-day precipitation), R10mm (Annual count of days where daily precipitation is more than 10 mm), R20mm (Annual count of days where daily precipitation is more than 20 mm), CDD (Consecutive dry days), CWD (Consecutive wet days), and PRCPTOT (Annual total wet day precipitation) have been analyzed via the optimal fingerprint method. The results revealed that Rx1day, Rx5day and CWD increased, while R10mm, R20mm, CDD, and PRCPTOT decreased among which CDD and Rx1day indices with values of 18.4% and 10.9%, respectively showed significant variations. Furthermore, the obtained results implied that only the effect of anthropogenic forcing with a value of 1.4 was detected and attributed in CDD variations, also ANT caused increase in the return period of a 20-year event by 1.9 year for CDD. Although human-induced forcing factors presented marked trends in some cases, their effects were not generally detected and attributed on the change in the observations, apart from one exception.