Akademik Veri Yönetim Sistemi
9 th International Symposium on Atmospheric Sciences – ATMOS 2019, İstanbul, Türkiye, 23 Ekim 2019, ss.201-212
Nonstationarity Impacts on Extreme Daily Precipitation and Temperature in Turkey
Rizwan Aziz and Ismail Yucel
1Middle East Technical University
Engineering Faculty, Civil Engineering Department, Water Resource Lab. rizvanazeez@yahoo.com, iyucel@metu.edu.tr
ABSTRACT
This study investigates the impacts of nonstationarities on yearly and seasonal hydroclimatological
extreme variables throughout Turkey as the assumption of stationarity can be problematic in frequency
analyses. GEV, gumbel, normal and lognormal for precipitation and GEV, gumbel and normal for
temperature were used with and without the nonstationarity assumption. The regions with positive and
negative impacts from nonstationarity were identified using observed and projected period for 2050- 2100 from twelve-member ensemble of CORDEX regional climate models. Evaluation of CORDEX
models for precipitation suggests that for most of the region in Turkey, RCMs originated from GCMs
EC-EARTH and HadGEM2-ES showed better agreement with observation as compared to RCMs
originated from other GCMs. For temperature, HadGEM2-ES and - CCLM4-8-17 was generally found
to be the better model. For all variables, GEV distribution fits to observation better than other
distributions. During historical period generally in Turkey, and particularly in the eastern part, nonstationarity impacts are positive on yearly as well as seasonal temperature maxima (up to 5) °C and
minima (up to 10) °C. These impacts are amplified during projection period. Similarly, nonstationarity
impact analyses of precipitation have shown generally positive impacts (up to 50 %) for yearly
maxima but many stations particularly in South-Eastern Anatolia, Central Anatolia, and Eastern
Anatolia were found to be under the influence of negative impacts (up to 40 %). Mostly positive
impacts were observed during the projection period for yearly as well as seasonal precipitation
maxima. In the long term, milder minimum temperatures throughout the country may contribute to
less snowpack in mountainous regions and, thus more precautions should be given to water
conservative planning under changing climate. Keywords: nonstationarity, ensemble, climate change