Impacts of climate change on rainfall indices estimation in western sub-basins of Iran

The purpose of this study was to document changes in indices simulated by the ensemble application of Coupled Model Inter-comparison Project CMIP5 and CMIP3 when analyzing impacts of climate change on catchment rainfall indices in sub-basins of Hamedan province, west of Iran. The analysis of the precipitation indices consisted of simple rainfall intensity, very heavy rainfall days, maximum one-day rainfall, and rainfall frequency. I investigated the relative change in three rainfall indices based on general circulation models (GCMs) under a mixture of greenhouse gas emission scenarios A1B and B1, RCP8.5 and RCP8.5 for two future periods 2020–2045 and 2045-2065. Results showed that each of the rainfall indices differed in stations under the three GCMs models (GIAOM, MIHR, MPEH5) and emission scenarios A1B, B1, RCP2.5, and RCP8.5. Relative 50y change for future periods 2046–2065 varied from -9.93% to 25% for daily intensity index, from 20.71% to 25.9% for very heavy rainfall days and from -15.71% to 13% for annual rainfall depth in the study area. Rainfall indices projection of sum of wet days, days>1mm, and maximum one-day rainfall showed decrease under the scenarios B1 and A1B and also sum of wet days, simple daily intensity, and heavy rainfall days>10 decreased under the RCP2.6.