The temporal variability in yearly and seasonal extreme precipitation across Turkey is investigated using stationary and nonstationary frequency approach. Four frequency distributions namely, generalized extreme value (GEV), gumbel, normal, and lognormal distributions are used for the historical period (1971–2016) as well as the projection period (2051–2100). The nonstationarity impacts are determined by calculating the percentage difference of return levels (30 years) between stationary and nonstationary cases for both periods. The results are presented as nonstationarity impact maps across Turkey, providing information about the spatial variability of the magnitude of impacts as well as the impact types, i.e., the increase or decrease in return levels of extreme precipitation. For nonstationarity analysis during the projection period, the projected precipitation data is obtained from a 12-member ensemble of the Coordinated Regional Downscaling Experiment (CORDEX) regional climate models (RCM) based on the worst emission scenario (RCP8.5). In addition to this, the effects of bias-corrections on stationarities are also investigated for selected RCMs. Performance evaluation of CORDEX ensemble members suggested significant intramodel and intraregion variability in the simulation of historical precipitation. Overall, GEV provided the best fit while normal distribution provided the worst fit to precipitation extremes. However, with a few exceptions, all the distributions exhibited a similar pattern for the historical impacts of nonstationarities across the country. The yearly nonstationarity impacts for the 30-year return level reached 35, 30, 25, and 20% for the Mediterranean, Aegean, Marmara, and Black sea regions, respectively, while a mixed type of nonstationarity impacts was found in Central, Eastern, and South-Eastern Anatolia regions. Moreover, the magnitude and impact type of nonstationarity showed important variations between the seasons. The ensemble analyses of CORDEX-based projected precipitation demonstrated that during the projection period, the nonstationarity impacts are found to be different in magnitude and type as compared to the impacts during the historical period in many regions (particularly in the eastern part of Turkey). The 30-year return levels of extreme precipitations are expected to increase (up to 30%) across Turkey in the yearly, winter, spring, and autumn seasons during the projection period. However, during the same period, the summer extremes in Eastern Anatolia and Mediterranean regions decreased ( up to 30%) with nonstationarity. Projected increases in the precipitation extremes lead to more floods and winter storms, while decreases in the summer precipitations will further dwindle water availability.

使用固定和非固定频率方法研究了土耳其全年和季节性极端降水的时间变化。历史时期（1971–2016）和预测时期（2051-2100）使用了四个频率分布，即广义极值（GEV），gumbel，正态和对数正态分布。非平稳性影响是通过计算两个时期的平稳性和非平稳性案例之间的回报水平（30年）的百分比差异来确定的。结果以整个土耳其的非平稳性影响图的形式显示，提供了有关影响程度的空间变异性以及影响类型的信息，即极端降水的回报水平的增加或减少。对于预测期内的非平稳性分析，预计的降水数据是根据最坏排放情景（RCP8.5）从12个成员组成的区域协调降尺度实验（CORDEX）区域气候模型（RCM）中获得的。除此之外，对于选定的RCM，还研究了偏差校正对平稳性的影响。CORDEX集合成员的性能评估表明，在模拟历史降水过程中，模型内部和区域内部存在明显的变异性。总体而言，GEV提供了最佳拟合，而正态分布提供了与极端降水最差的拟合。但是，除了少数例外，所有分布对于全国非平稳性的历史影响都表现出相似的模式。地中海地区30年回报水平的年度非平稳性影响达到了35％，30％，25％和20％，分别是爱琴海，马尔马拉和黑海地区，而在安纳托利亚中部，东部和东南部地区则发现了混合的非平稳性影响。此外，非平稳性的程度和影响类型在各个季节之间显示出重要的变化。基于CORDEX的预计降水的整体分析表明，在预测期内，与许多地区（特别是在土耳其东部）的历史时期相比，非平稳性影响的程度和类型有所不同。在预测期内，整个土耳其的30年极端降水的回归水平预计将在每年，冬季，春季和秋季的整个季节增加（高达30％）。但是，在同一时期，由于不稳定，东部安纳托利亚和地中海地区的夏季极端事件减少了（最多30％）。预计极端降水量的增加将导致更多的洪水和冬季风暴，而夏季降水量的减少将进一步减少水的供应。