Impacts of climate change on spatial drought distribution in the Mediterranean Basin (Turkey): different climate models and downscaling methods

Abstract

The impacts of climate change increasingly show themselves in many forms in our everyday lives such as heatwaves and droughts. Drought is one of the critical events today for increasing drought frequency. This study focuses on meteorological drought because it directly affects other drought types. Hence, this study focuses on how the future drought conditions will vary under climate change effects in the Mediterranean basin. In doing so, this study utilizes precipitation data of three General Circulation Models (GCMs) and three Regional Circulation Models (RCMs). The GCMs are CNRM-CM6, GFDL-CM4, and MPI-ESM1, while the RCMs are CNRM-CM5, GFDL-ESM2M, and MPI-ESM-MR. Mitigating biases of the climate models, this study utilizes four Statistical Downscaling methods (SD), linear scaling (LS), local intensity scaling (LOCI), power transformation (PT), and distribution mapping (DM). Here, the study has two purposes. First, it compares the performances of SD methods in improving climate models' representation of observed climate variables. Second, the study shows how different methods will affect spatial drought distribution in the area under SSP2 RCP4.5 and RCP8.5 scenarios.Consequently, the study uses the Standardized Precipitation Index (SPI) and Z-score Index (ZSI) to quantify future drought conditions and reaches the following results. The study reveals that mild drought conditions are prevalent in the basin for future periods, and drought indices go down to -0.55. The study also shows that different SD methods affect the results obtained by each climate model diversely. For example, while the LS method causes the most drought conditions on the results based on CNRM-CM5 and CNRM-CM6, the DM method has a similar impact on outcomes based on GFDL-CM4 and GFDL-ESM2M and causes the most drought conditions.