Investigation of hydro-meteorological droughts in the Aegean region under the influence of climate change

In recent years, due to the ever-increasing greenhouse gas emissions from destructive human activities, we have been witnessing widespread and rapidly increasing climate change, with devastating consequences such as warmer weather and numerous droughts in many parts of the world. Turkey is also affected by these negative changes. Therefore, it is vital to assess the drought that will be experienced in the future and to consider the necessary measures to minimize its negative impacts on human life and other living organisms. Therefore, in this study, it was decided to investigate and predict the amount of meteorological drought in the Aegean Region until 2100. For this purpose, firstly, the data of 10 meteorological stations (Çeşme, İzmir, Manisa, Muğla, Nazilli, Seferihisar, Sultanhisar, Selçuk, Uşak, Yatağan, Çeşme, İzmir, Manisa, Muğla, Nazilli, Seferihisar, Sultanhisar, Selçuk, Uşak, Yatağan) in Büyük Menderes, Küçük Menderes and Gediz basins of the Aegean region between 1975-2014 were analyzed, In addition, the meteorological behavior of the region from past to present has been studied using four climate models (AWI-CM-1-1-MR (Germany), NorESM2-MM (Norway), EC-Earth3-CC (Europe), CNRM-CM6-1-HR (France)) and two climate change scenarios (SSP2-4. 5 and SSP5-8.5). As a result, two methods have been used to predict the number of future dry months, namely the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) indices, both of which are nowadays modern and common methods with acceptable accuracy. SPI and SPEI are widely used drought indices. The SPI is derived from precipitation data only, while the SPEI includes both precipitation and evapotranspiration data. While the SPI is traditionally calculated on a monthly scale, the SPEI can be calculated on different time scales, such as 6 to 24 months. Recent studies have shown that SPEI may be more suitable for monitoring periods of drought under climate change as it takes into account potential increased evapotranspiration in a warmer climate. As a results, it can be concluded that in the future (by 2100) each and every region of the region will be subjected to droughts. The results show that although this region has been one of the wettest and most humid regions of Turkey for almost all of its history, it is currently subjected to numerous droughts and will be rapidly moving towards prolonged and severe droughts in the future with a short period of time. For example, according to the forecasts, Seferihisar station will be exposed to 250 months of drought in the years (2069-2099) or Yatağan station is projected to experience 200 months of drought in the same time period. Under the same conditions, Çeşme station will experience close to 250 dry months. It will therefore be important for Turkey to take measures to combat climate change and implement sustainable policies to deal with these problems. Because it will negatively affect the health, agriculture and economy, in the near future. Keywords: Climate change, Drought, Shared Socioeconomic Pathways (SSP), Global climate model (GCM), Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI).