Observed changes and trends in heatwave characteristics in Turkey since 1950

This study investigated the spatiotemporal changes, including long-term trends and abrupt changes in the heatwave (HW)-related climatic characteristics of Turkey, such as the heatwave number (HWN), duration (HWD), frequency (HWF), magnitude (HWM), and amplitude (HWA). Heatwave-related indices in Turkey based on 88 meteorological stations were calculated considering the 90th percentile of the daily minimum air temperature (Tn90p) and the 90th percentile of the daily maximum air temperature (Tx90p). Trend analysis of the heatwave characteristics indicated that Turkey has experienced more frequent, longer, and hotter heatwaves since 1950. The most significant increasing trends observed in the series of HWNs, HWFs, and HWDs and the Tn90p series were characterized generally with greater trend values. Geographically, the largest changes in the heatwave characteristics of Turkey were detected to occur after the middle of the 1990s in the Black Sea and the Mediterranean coasts, which are in agreement with previous studies performed for various regions of the Mediterranean basin. Long-term trends in almost all country-based heatwave indices of Turkey, except trends in the Tn90p series of HWM values, particularly the Tn90p and Tx90p time series of HWN, HWF, and HWD, and the Tn90p time series of HWA values are statistically significant at the 0.000 level. Statistical comparisons of the means and variances of the Tn90p and Tx90p time series of HWN, HWF, and HWD between the periods of 1950-1984 and 1985-2018 are statistically significant at the 0.005 level. These results indicate abrupt changes towards increased heatwave conditions after the year 1984.