THE SCIENCE OF THE TOTAL ENVIRONMENT AN INTERNATIONAL JOURNAL FOR SCIENTIFIC RESEARCH INTO THE ENVIRONMENT AND ITS RELATIONSHIP WITH MAN, cilt.912, ss.1-20, 2024 (SCI-Expanded)
Precipitation, especially in regions dominated by the Mediterranean climate, is one of the most critical parameters
of the hydrological cycle and the environment affected by climate change. One the one hand, the transition
probabilities of wet and dry days in precipitation occurrence are a relatively new topic, on the other hand these
are essential in defining the regional climate. For the first time, spatiotemporal variations of transition probabilities
of wet and dry days in the Susurluk Basin, northwestern Türkiye, dominated by a semi-arid Mediterranean
climate and also having a mountain climate, were analyzed based on the observation (1979–2014) and
future terms (2030–2059 as short and 2070–2099 as long), under four Shared Socioeconomic Pathways (SSPs)
scenarios. To do this, statistical downscaling was performed for 14 general circulation models (GCMs) from the
CMIP6. By applying an ensemble of four high-performing GCMs, four indices for transition probabilities of wet
and dry, i.e., a dry day following a dry day (FDD), a wet day following a dry day (FDW), a dry day following a
wet day (FWD), and a wet day following a wet day (FWW), were calculated, and their changes were determined
statistically. Monotonic and partial trends of the indices were also analyzed. According to the results, the FDD will increase in water year and wet period and autumn in the future, especially for the long term, in the basin
dominated by the FDD (75 % in water year). The risks are higher in the western part of the basin, where human
activities are intense, as the FDD is higher in this part than other parts especially in summer (90–100 %) in SSP3-
7.0 and SSP5-8.5 scenarios for the long term. So, the length of consecutive dry days in the wet period and water
year will increase in the basin, thus increasing the likelihood of droughts. As for the intra-term trends, the FDD
increases and the FWW decreases in the water year and seasons in SSP3-7.0 and SSP5-8.5, contrary to the
observation term.