Abstract This study investigates the temporal variability in yearly and seasonal extreme temperatures across Turkey using stationary and nonstationary frequency analysis. The analyses are conducted using Generalized Extreme Value (GEV), Gumbel and Normal distributions for minimum and maximum temperatures during historical (1971–2016) and projection period (2051–2100). The future nonstationarity impacts are quantified using a 12-member ensemble of The Coordinated Regional Downscaling Experiment (CORDEX) regional climate models (RCM) based on the worst emission scenario (RCP8.5). The ability to preserve the nonstationarity signals after bias-correction for selected RCMs are also presented. CORDEX ensemble members generally underestimated the temperature across all seven geographical regions of Turkey. The CORDEX-31 (HadGEM2-ES/CCLM) provided the most trustable temperature simulation in each region. GEV and Normal distributions exhibited a closer fit to each other but both distributions showed substantially better fit than Gumbel distribution for temperature extremes. Magnitudes of nonstationarity impacts (30-year return level) show strong spatial and seasonal variability. Notably higher magnitudes are observed for minimum temperature (up to +10 °C) than maximum temperature (up to +4 °C). Such positive impacts are more significant particularly in eastern Turkey for yearly and seasonal scales. This effect shows greater regional variability in the historical period but with increased temperature projection it is more homogenous and larger in the future period for each region. In the long term, nonstationarities, particularly in minimum temperatures might contribute to less snowpack, accelerate the time-shifts towards the earlier days of the year in snowmelt runoff peaks of streams, further dwindle the water availability during the summer season.

中文翻译：

---

非平稳性对土耳其年度和季节性极端温度频率分析的影响

摘要 本研究使用平稳和非平稳频率分析调查了土耳其每年和季节性极端温度的时间变化。这些分析是使用广义极值 (GEV)、Gumbel 和正态分布对历史 (1971-2016) 和预测期 (2051-2100) 期间的最低和最高温度进行的。使用基于最坏排放情景 (RCP8.5) 的协调区域降尺度实验 (CORDEX) 区域气候模型 (RCM) 的 12 成员集合对未来的非平稳性影响进行量化。还介绍了在对选定的 RCM 进行偏差校正后保留非平稳性信号的能力。CORDEX 合奏成员普遍低估了土耳其所有七个地理区域的温度。CORDEX-31 (HadGEM2-ES/CCLM) 提供了每个区域最可靠的温度模拟。GEV 和正态分布表现出彼此更接近的拟合，但对于极端温度，这两种分布都表现出比 Gumbel 分布更好的拟合。非平稳影响的大小（30 年回报水平）显示出强烈的空间和季节性变化。观察到的最低温度（最高 +10 °C）明显高于最高温度（最高 +4 °C）。这种积极影响在年度和季节性范围内尤其在土耳其东部更为显着。这种效应显示了历史时期更大的区域变异性，但随着温度预测的增加，它在未来时期内每个区域的同质性和更大。长期来看，非平稳性，