Comparisons of historical CMIP5 and CMIP6 protocols for the drought indices of Turkey

Located in the semi-arid region, Turkey is much more vulnerable to the drought effects of climate change. It is expected that the severity, duration, and frequency of drought episodes will increase due to climate change. The observations reveal that the drought episodes in Turkey have increased dramatically over the last decade. For example, in 2020, the occupancy rates of dams in Istanbul dropped below 30%. Therefore, the accuracy of the projections of climate models is essential in developing adaptation strategies related to drought types. Therefore, the study aims to compare the bias of the runoff and moisture content of the climate projection models (NorESM1-M and NorESM2; FGOALS-g2 and FGOALS-g3; and GFDL-CM3 and GFDL-CM4) with the observations. In addition, the scenarios in the CMIP5 and CMIP6 protocols were compared by calculating the probability distribution functions of the flow data for ten-year periods. In addition, consecutive dry days index (ECACDD), warm spell duration index (ECAHWFI), water storage deficit index, and Palmer drought severity index are also analyzed. Preliminary conclusions indicate that climate models vary significantly in capturing historical events. For this reason, an ensemble of the models needs to be created for decision-making purposes.