Long-term spatio-temporal trends and periodicities in monthly and seasonal precipitation in Turkey

This study aimed to provide broad insight into the long-term trends and periodicity of monthly and seasonal precipitation in Turkey and to evaluate their implications for sectoral water availability. Overall, Turkey’s monthly precipitation declined over the last five decades. While decreasing precipitation trends were dominant in the wet season, consistently increasing trends prevailed in the dry season. The monthly monotonic trends were marked by larger downward trends, especially in early winter and spring. The trend magnitudes in annual and wet season precipitation decreased from north to south and west to east, reaching a maximum value of 7.5 mm/year increase in the eastern Black Sea. The magnitude of dry season trends was much smaller but consistent across the country, varying by 1–5 mm/year. Monthly changes in the trend magnitudes varied between − 2.2 and 3.4 mm, reflecting both decrease and increase, respectively. The magnitude of the downward precipitation trends was higher in inland regions than in other regions. Spatial patterns in the trends evidenced that wet season precipitation variability largely governs annual precipitation variability. The wavelet spectrum indicated a strong annual signal for the monthly precipitation. The inland regions experienced the periodicity of wet years at much longer durations. An average 8-year periodicity was dominant for the annual precipitation, underlining its inter-annual variability and coincided well with the NAO spectrum. Assuming the identified trends persist in the future, a further increase in the magnitude of precipitation trends in coastal areas can enhance the flood risk. However, the precipitation decreases during the wet season are bound to have adverse consequences on sectoral-dependent water availability.