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    Öğe
    Multifractal characterization of meteorological droughts in Turkiye's mediterranean region using visibility graph approaches
    (Springer, 2026) Simsek, Oguz; Zeybekoglu, Utku; Plocoste, Thomas; Adarsh, S.
    This study introduces a novel framework based on visibility graph (VG) and its upside-down variant (UDVG) to assess the multifractal structure of meteorological droughts in Turkiye's Mediterranean region. Using the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) from 24 stations (1970-2022), we examined drought dynamics across time scales ranging from 1 to 24 months. The analysis shows that except for a few one-month cases, drought indices exhibit predominantly stochastic rather than chaotic behaviour, validating the use of multifractal tools. VG and UDVG approaches were then applied to 3-, 6-and 12-month series, and multifractal spectra were computed via the sandbox and Chhabra-Jensen methods. Results indicate that SPEI consistently displays stronger multifractality than SPI, confirming the added role of evapotranspiration in drought variability. The UDVG framework reduced the multifractal spread (Delta Dq = D-0-D-2) by similar to 30% compared to VG (mean Delta Dq = 0.49 vs. 0.72), highlighting its sensitivity to low-amplitude, persistent droughts. In contrast, VG emphasises high-magnitude wet-dry fluctuations. This dual-network approach therefore provides complementary perspectives: VG is better suited to identifying extreme wet conditions, while UDVG can capture low amplitude fluctuations, which are cautionary sign leading to long term drought and its small changes can be early indicators of drought disasters. Overall, the proposed VG/UDVG-based multifractal framework provides novel insights into drought complexity and has the potential to support the development of early warning systems and adaptation strategies in Mediterranean-type climates.
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    Öğe
    Relationship between Mediterranean region temperatures and precipitation with atmospheric oscillations and ITA results
    (Springer, 2025) Zeybekoglu, Utku; Simsek, Oguz; Durgun, Emir Cengiz
    This study analyzes the relationship between precipitation and temperature data measured in the Mediterranean Region of Turkey from 1970 to 2022, and the Mediterranean Oscillation Indexes (MOI1 and MOI2) and the Arctic Oscillation (AO). In the study, correlation analyses and Innovative Trend Analysis (ITA) methods were applied using data from 24 meteorological observation stations in the region. As a result of the correlation analyses, it was determined that AO had a negative correlation with the precipitation data of all stations in the region. This situation shows that the increase in AO values reduces the amount of precipitation. While a generally negative relationship exists between MOI1 and precipitation from the two versions of MOI, a mostly positive relationship was determined between MOI2 and precipitation. However, statistically significant relationships were determined in some stations. When evaluated in terms of temperature, negative correlations were determined with MOI1, MOI2, and AO indices in all stations in the region. This situation shows that atmospheric oscillations effectively influence temperature changes and that fluctuations in temperature values may be mainly due to these atmospheric systems. When the ITA results were examined, a significant increasing trend in temperature data was observed. However, there was no stable increasing or decreasing trend in precipitation data. While an increasing trend was observed in small and medium-sized precipitation in the Western Mediterranean, a decreasing trend was observed in large precipitation. In the Eastern Mediterranean, changing trends were detected at different stations. These results reveal that the risk of drought may increase due to rising temperatures in the region, and strategic planning should be implemented for water resource management. As a result, the study's findings indicate that atmospheric oscillations, such as the Mediterranean Oscillation (MOI) and the Arctic Oscillation (AO), significantly affect precipitation and temperature regimes in the Mediterranean Region of Turkey. The increase in temperature in the region may increase the pressure on water resources in the future and cause drought events to occur more frequently. In this context, reviewing regional water management policies and developing sustainable water use strategies is important.