Spatio-temporal evaluation of various global circulation models in terms of projection of different meteorological drought indices

During the coming years, a dramatic increase is expected in the number of drought events mainly due to climate change. In this study, the spatio-temporal variations of duration and intensity of drought events during two 30-year periods in the future (2040–2069 and 2070–2099) together with the reference period (1971–2000) were investigated based on the impacts of climate change. Three drought indices including the Standardized Precipitation Index, the China Z Index, and the Statistical Z Score were calculated from the dynamically downscaled precipitation data from the outputs of GFDL-ESM2M, HadGEM2-ES, and MPI-ESM-MR general circulation models (GCMs) under RCP4.5 and RCP8.5 scenarios over the Western Black Sea (WBS) and the Euphrates–Tigris (ET) basins in Turkey. The biases in the GCMs' precipitation were corrected using the linear scaling method. Additionally, the Mann–Kendall trend test was adapted to the values of drought indices to detect the trend. The results of the study showed that there is no meaningful variation between the different drought indices and also the outputs of various GCMs in terms of drought properties. On the other hand, based on the drought indices values calculated from the outputs of all GCMs, it was found that drought duration and intensity will increase during the current century. Additionally, it was concluded that by taking the spatial distribution of drought properties over the basins into the account, there is a slight relationship between the geographical elevation and drought properties over the WBS and the ET basins.