Temporal and spatial variation of rainfall in Iran under climate change until 2100

In this research, the long-term effect of climate change on the spatial and temporal distribution of precipitation in Iran was investigated under A1B, A2 and B1 scenarios up to 2100. The LARS-WG model calibrated by daily precipitation data from 52 synoptic stations for the reference period (1980-2100) was used for downscaling the HADCM3 atmospheric general circulation model data under the mentioned scenarios up to 2100. The spatial distribution maps of precipitation changes were prepared in GIS environment. Low root mean square error (RMSE) and high efficiency factor (EF) values for comparing the observed and simulated precipitation, demonstrates the ability of LARS-WG for precipitation simulation. Simulation results showed that climate change causes a non-uniform precipitation increase for both spatial and temporal scales in a major part of the country. The precipitation increase over the Caspian Sea, Oman Sea and Persian Gulf coasts, western hillsides of the Zagros Mountains and northern hillsides of the Alborz Mountains was higher than that in the central, eastern and north-eastern parts. Despite a positive significant increasing trend in rainfall during 1980-2100, a decreasing trend was observed in rainfall during 2010-2100 so average rainfall during 2041-2070 and 2071-2100 was lower than one for 2011-2040. These results emphasize on the need for planning to optimally use of green water in the country.