Nonstationarity Impacts on Extreme Daily Precipitation and Temperature in Turkey

Aziz R., Yücel İ.

9 th International Symposium on Atmospheric Sciences – ATMOS 2019, İstanbul, Turkey, 23 October 2019, pp.201-212

  • Publication Type: Conference Paper / Full Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.201-212
  • Middle East Technical University Affiliated: Yes


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., 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