فهرست نشریات علمی دسترسی آزاد ایران

Relative humidity is an essential climatic parameter with direct implications for environmental studies and water resource management. Despite its importance, long-term variability in relative humidity remains less explored in many semi-arid river basins. This study aimed to detect trends in relative humidity in the Darreh Dozdan River Basin, Iran, over the period 1998–2022. To achieve this, four complementary methods were applied at monthly and annual scales, including the Mann–Kendall trend test, Sen’s slope estimator, Pearson correlation, and linear regression.  The analysis revealed that only two months, January and May, exhibited statistically significant trends. January showed a consistent decline, with relative humidity decreasing by about 0.39% per year (Mann–Kendall Z = –2.06; Pearson r = –0.47; p = 0.02). In contrast, May displayed an increasing trend of approximately 0.51% per year (Z = 2.18; Pearson r = 0.40; p = 0.05). No other months indicated significant changes, and the annual trend analysis confirmed remarkable stability, with no detectable long-term increase or decrease in relative humidity during the 25 years. These findings suggest that while annual humidity has remained stable, seasonal shifts are emerging. Such insights are valuable for climate monitoring and for guiding adaptive water management strategies.