Trend analysis of maximum rainfall series of standard durations in Turkey with innovative methods

Information about temperature and rainfall, the main elements of the Earth's climate, is essential in determining the characteristics of world climate variations. The changes in these two parameters, which show significant variability in both spatial and temporal scales, reveal essential clues for understanding the general structure of the climate. This study aims to investigate the effect of climate change on the annual maximum (extreme) rainfall values observed in Turkey. In this context, trend analyses were performed using Mann-Kendall (MK) test, innovative trend analysis (ITA), and improved visualization of ITA (IV-ITA) methods to the standard durations (t = 5, 10, 15, 30 min, and 1, 2, 3, 4, 5, 6, 8, 12, 18, 24 h) of the annual maximum rainfalls of 82 stations located in seven geographical regions of Turkey between 1975 and 2015. Trends for low and high maximum rainfall values were determined with IV-ITA. According to the MK test, there was an increasing trend of 15% in all stations, while only a decreasing trend of 1% was detected. Besides, the ITA method determined these values as 63% and 17%, respectively. The trends for low and high category values in the IV-ITA method are consistent, with approximately 60% increasing and 20% decreasing trends. An increasing trend is dominant throughout Turkey, and this trend is concentrated in the Black Sea, Marmara, and Aegean regions. Medium- and long-duration rainfall tended to increase, while short-duration rainfall tended to decrease.