Sürdürülebilir Kalkınma Amaçları
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- MakaleAçık Erişim2026Scopus SJRQ4Development of the seasonal non-monotonic Mann-Kendall test for hydroclimatic data
Şan, Murat
Climate change can show different characteristics at low and high values of a time series, leading to non-monotonic trends. The Mann-Kendall (MK) and seasonal MK tests can only detect monotonic trends and ignore different behaviors in low and high value groups. To overcome this limitation, extending the recently proposed non-monotonic MK (NMK) test, the seasonal NMK (SNMK) test is proposed. The method was applied to four stations in Türkiye with four different climatic and topographic characteristics using monthly total precipitation data for the 1969-2020 for seasonal trend behavior. The results showed that while no significant trends were detected in entire time series, intra-seasonal and annual data, both monotonic and non-monotonic significant trends emerged in seasonal analyses. Especially in two stations, opposite changes in low and high values, increased seasonal variance and non-monotonic seasonal trends were observed. The test can be used for regional trend analysis by replacing seasonal data with regional data. It is also predicted that the SNMK test can be used as an effective decision support tool in areas with high seasonality such as water resources management, agriculture, energy planning and disaster management.
- MakaleYalnız künye2023Scopus SJRQ1Trend analysis of precipitation using innovative approaches in northwestern Turkey
Körük, Ali Emre; Kankal, Murat; Yıldız, Mehmet Berkant; Akçay, Fatma; Şan, Murat; Nacar, Sinan
Precipitation is highly sensitive to climate change, and monitoring its trends over time is essential for understanding the effects of global warming on the Earth's water cycle. This study investigates the effects of climate change on monthly precipitation in the Susurluk Basin located in northwestern Turkey, using innovative trend analysis methods. Innovative Polygon Trend Analysis (IPTA) using star graphics and Improved Visualization for Innovative Trend Analysis (IV-ITA) techniques were used to analyze precipitation data from nine stations in the basin over 50 years (1970–2019), and the findings were compared to classical Mann-Kendall (MK) results. According to the trend analysis results, the MK method detected significant trends in only two months in the decreasing direction. In these decreasing trends observed at Simav and Keles stations in November, z values were calculated as −2.38 and −2.05, respectively. IPTA method detected increasing trends in 54 months and decreasing trends in 40 months; this means there is a change of more than 5% between two half series. The IV-ITA method indicated an increase of more than 40% in the low values for January, March, August, and September. In addition, there was an increasing trend of more than 40% in the high values observed in September at all stations. It was observed that mean precipitation heights increased from September to December and then decreased throughout the basin. It is predicted that decreases in precipitation during dry seasons may put intense pressure on agricultural water use and affect water quality. In addition, the increase in precipitation in spring months may increase flood events. It was determined that graphical innovative trend analysis methods are more effective in trend identification than MK, and these methods' results have much higher visual inspection and linguistic interpretation possibilities. Innovative methods allow for more flexible and in-depth analysis using different statistical parameters.
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