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Nonstationary analysis of the extreme temperatures in Turkey
Dynamics of Atmospheres and Oceans ( IF 1.7 ) Pub Date : 2021-07-03 , DOI: 10.1016/j.dynatmoce.2021.101238
Hakan Aksu 1
Affiliation  

Record-breaking extreme temperatures have been measured in the last two decades all over Turkey, with recent studies detecting positive trends in extreme temperature time series. In this study, nonstationary extreme value analysis was performed on extreme temperature time series obtained from fifty stations scattered over the seven geographical regions of Turkey. Basic characterization of the data set was defined through outlier detection, homogeneity, trend detection, and stationarity tests. Trend-including non-stationary extreme temperature time series were analyzed with non-stationary Generalized Extreme Value distribution. Three main physical drivers were considered as the leading causes that trigger the observed trends in extreme temperatures over Turkey: time, teleconnection patterns of the Arctic Oscillations, and those of the North Atlantic Oscillations. The results showed that most of the absolute annual minimum and maximum temperature time series are inhomogeneous while the possible breakpoints date back to the1970s and 1990s, respectively. More than half of the absolute annual maximum time series (26/50 and many of the absolute annual minimum time series (21/50) showed a positive trend. No negative trend was detected in the extreme temperature time series. Based on the frequency analysis of the 21 annual maximum time series, the non-stationary estimations of 50-year return levels were detected to be higher than in the stationary model (between 0.44 °C and 3.73 °C). The return levels in 15 of the 20 minimum temperature time series increased from 0.11 °C up to 12.28 °C. Elevation increases the nonstationarity impact on absolute minimum temperatures and decreases it on absolute maximums. The findings in this study indicate that the consideration of non-stationarity in extreme temperature time series is a necessity during return level estimations over the study area.



中文翻译:

土耳其极端温度的非平稳分析

在过去的二十年里,土耳其各地都测量到了破纪录的极端温度,最近的研究发现了极端温度时间序列的积极趋势。在这项研究中,对分散在土耳其七个地理区域的五十个站点获得的极端温度时间序列进行了非平稳极值分析。数据集的基本特征是通过异常值检测、同质性、趋势检测和平稳性测试来定义的。用非平稳广义极值分布分析包含趋势的非平稳极端温度时间序列。三个主要的物理驱动因素被认为是触发观察到的土耳其极端气温趋势的主要原因:时间、北极涛动的遥相关模式、和北大西洋涛动的那些。结果表明,大多数绝对年最低和最高温度时间序列是非均质的,而可能的断点分别可以追溯到 20 世纪 70 年代和 1990 年代。超过一半的绝对年最大时间序列(26/50和许多绝对年最小时间序列(21/50)呈正趋势。极端温度时间序列未检测到负趋势。基于频率分析)在 21 个年度最高时间序列中,检测到 50 年回归水平的非平稳估计值高于平稳模型(介于 0.44 °C 和 3.73 °C 之间)。20 个最低温度中的 15 个回归水平时间序列从 0.11 °C 增加到 12.28 °C。海拔增加了对绝对最低温度的非平稳性影响,并降低了对绝对最高温度的影响。本研究的结果表明,在研究区域的回归水平估计过程中,必须考虑极端温度时间序列的非平稳性。

更新日期:2021-07-06
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