Nonstationarity impacts on frequency analysis of yearly and seasonal extreme temperature in Turkey

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 degrees C) than maximum temperature (up to +4 degrees 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, non-stationarities, 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.


Assessing nonstationarity impacts for historical and projected extreme precipitation in Turkey
Aziz, Rizwan; Yücel, İsmail (Springer Science and Business Media LLC, 2021-01-01)
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 c...
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Yozgatlıgil, Ceylan (Wiley, 2018-12-01)
Monthly maximum precipitation amounts for the period 1950-2010 were modelled for seven climatological stations in the western Black Sea subregion of Turkey using a distributional and time series analysis approach. First, the generalized extreme value (GEV) distribution was fitted using the location parameter of the GEV distribution as a function of several explanatory variables that affect the maximum precipitation. We quantified the change in extreme precipitation for each location and derived estimates of...
Intercomparison of rain gauge, radar, and satellite-based precipitation estimates with emphasis on hydrologic forecasting
Yılmaz, Koray Kamil; Hsu, KL; Sorooshian, S; Gupta, HV; Wagener, T (American Meteorological Society, 2005-08-01)
This study compares mean areal precipitation (MAP) estimates derived from three sources: an operational rain gauge network (MAPG), a radar/gauge multisensor product (MAPX), and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) satellite-based system (MAPS) for the time period from March 2000 to November 2003. The study area includes seven operational basins of varying size and location in the southeastern United States. The analysis indicates that agre...
Clustering current climate regions of Turkey by using a multivariate statistical method
İyigün, Cem; Batmaz, İnci; Yozgatlıgil, Ceylan; Koc, Elcin Kartal; Ozturk, Muhammed Z. (Springer Science and Business Media LLC, 2013-10-01)
In this study, the hierarchical clustering technique, called Ward method, was applied for grouping common features of air temperature series, precipitation total and relative humidity series of 244 stations in Turkey. Results of clustering exhibited the impact of physical geographical features of Turkey, such as topography, orography, land-sea distribution and the high Anatolian peninsula on the geographical variability. Based on the monthly series of nine climatological observations recorded for the period...
Multiregional Satellite Precipitation Products Evaluation over Complex Terrain
Derin, Yagmur; Anagnostou, Emmanouil; Berne, Alexis; BORGA, Marco; BOUDEVILLAIN, Brice; BUYTAERT, Wouter; CHANG, Che-Hao; DELRIEU, Guy; HONG, Yang; HSU, Yung Chia; LAVADO-CASIMIRO, Waldo; MANZ, Bastian; MOGES, Semu; NIKOLOPOULOS, Efthymios I.; SAHLU, Dejene; SALERNO, Franco; RODRIGUEZ-SANCHEZ, Juan-Pablo; VERGARA, Humberto J.; Yılmaz, Koray Kamil (American Meteorological Society, 2016-06-01)
An extensive evaluation of nine global-scale high-resolution satellite-based rainfall (SBR) products is performed using aminimumof 6 years (within the period of 2000-13) of reference rainfall data derived from rain gauge networks in nine mountainous regions across the globe. The SBR products are compared to a recently released global reanalysis dataset from the European Centre for Medium-Range Weather Forecasts (ECMWF). The study areas include the eastern Italian Alps, the Swiss Alps, the western Black Sea ...
Citation Formats
R. Aziz, İ. Yücel, and C. Yozgatlıgil, “Nonstationarity impacts on frequency analysis of yearly and seasonal extreme temperature in Turkey,” ATMOSPHERIC RESEARCH, pp. 0–0, 2020, Accessed: 00, 2020. [Online]. Available: