Spatial and temporal variation of meteorological parameters in the lower Tigris–Euphrates basin, Türkiye: application of non-parametric methods and an innovative trend approach

In this study, Mann–Kendall (MK), Spearman's rho (SR), and innovative trend analysis with significance test (ITA-ST) are performed on about 53 years of meteorological parameters obtained from 23 meteorological stations located in the lower Tigris–Euphrates basin (LTEB), Türkiye. Finally, sequential Mann–Kendall (SMK) and Cusum tests are applied to detect any abrupt changes in annual time series. Results indicate that MK and SR demonstrate a significant trend in seven of the total annual precipitation series, and ITA-ST captures the existence of a significant trend in 21 of the 23 total annual precipitations. Three methods reveal that there is an increasing trend in both the annual mean temperature and the annual total evapotranspiration (EP). MK, SR, and ITA-ST capture a significant decreasing trend in the 10, 8, and 16 of the 23 annual mean relative humidity (RH) series, respectively. According to the findings, ITA-ST is more sensitive than the classical MK and SR methods. Cusum and SMK tests are detected the start of trend year 21.7 and 8.6% of annual total precipitation, 95.65 and 69.56% of annual mean temperature, 47.82 and 17.4% of total mean RH, and 95.65 and 69.56% of annual total EP time series, respectively. The Cusum test is found to be more sensitive than the SMK test. HIGHLIGHTS The MK, SR, and ITA-ST tests were first used for the relative humidity.; Three different methodologies show that both the temperature and the evapotranspiration are on the rise.; The ITA-ST technique is more sensitive than conventional MK and SR techniques.; MK, SR, and ITA-ST display a significant decreasing trend in the annual mean relative humidity series.;