The effects of climate change on the drought trend of Varamin plain using De-Martonne index

Increasing greenhouse gas concentrations can lead to global warming and climate change. In this study, the trend of changes in precipitation and temperature of Varamin synoptic station during the period from 2021 to 2050 AD was investigated using the CMIP5 data of the Fifth IPCC Assessment (AR5). One of the major limitations of using these models is their low spatial resolution, which does not match the accuracy required by hydrological models in terms of space and time. Therefore, downscaling method by LARS-WG model was used to overcome this limitation. Finally, temperature and precipitation data were simulated under two scenarios of RCP2.6 and RCP8.5 for the Future period and compared with the base period. Due to the effect of temperature and precipitation on the future drought status of the plain, De-Martonne drought index was determined under two scenarios of climate change and compared with the base period. The results of the study showed the significant effects of climate change on the aggravation of conditions in the region and consequently a -1/3 degree of centigrade increase in temperature and change in precipitation pattern and changes in drought index. According to the obtained results, it can be stated that although the drought trend is affected by several factors, but in the shadow of possible climate change in the future there is a possibility of increasing the drought trend in Varamin plain, due to changes in rainfall and rising temperatures, so that both climate scenarios also predicted a drought condition for the study area.