Assessing Rainfall Trends and Change Points in Owerri, Nigeria: Implications of Climate Change

Abstract

This study aims to analyze long-term rainfall trends and change points in Owerri, Nigeria, to understand climate change impacts on local precipitation patterns. The study utilized daily annual maximum series (AMS) rainfall data spanning 31 years (1992-2022). The Indian Meteorological Department (IMD) model was employed to downscale the time series data into durations ranging from 5 minutes to 24 hours. The choice of IMD is based on availability in literature. Mann-Kendall (MK) trend and Sen's Slope Estimator (SSE) tests revealed a statistically insignificant decreasing trend across all durations. The Sen's Slope magnitude ranged from -0.0679 mm/year for 5-minute duration to -0.4474 mm/year for 24-hour duration, corresponding to a variation rate of -4.474 mm/decade for the 24-hour duration. While the trends in rainfall patterns are decreasing, they lack statistical significance, the. Also, trend change-point analysis, utilizing Distribution-free CUSUM and Sequential Mann-Kendall tests, identified 2013 and 2017 as potential change points in the rainfall pattern. These findings underscore the importance of continued monitoring to inform urban planning and water resource management in a climate-sensitive region.