Investigation of extreme precipitation indices in Turkey

This paper focuses on spatiotemporal characteristics of precipitation indices of Turkey's precipitation data for the periods 1966-2014. Seven precipitation indices include the number of extremely wet days, very wet days, heavy precipitation days (10 mm and 20 mm), simple daily intensity days, and consecutive dry and wet days. The indices are based on homogenized precipitation data. Besides, long-term changes and trends in the time series of precipitation indices in terms of climatic variability were investigated using nonparametric time series analysis methods. The results obtained are summarized as follows. Extremely wet and very wet day indices include significant decreasing trends in most stations. The trend is statistically significant at some stations in the Mediterranean region and southeastern Anatolia region. The number of heavy precipitation day indices tend to decrease in most of the stations in the Mediterranean precipitation zone, throughout Turkey. Simple daily intensity index generally displays an increasing trend. Consecutive dry days include an overall upward trend throughout Turkey. The inner and in the west of southeastern Anatolia regions have displayed a statistically significant increasing trend. Consecutive humid days tend to decrease overall outside of Turkey's internal parts. The study also examined the relationships between atmospheric oscillation indices and precipitation indices. Accordingly, the atmospheric oscillation index that has the most decisive effect on the Turkish precipitation indices is NAO.