Wavelet Analysis of Hydroclimatic Teleconnections and Precipitation Variability over Ethiopia

This study investigates the variability of precipitation across Ethiopia by analyzing monthly and annual rainfall data from five stations representing the north, east, west, south, and central regions over a 31-year period (1987–2017). The research applies the Standardized Precipitation Index (SPI) and continuous wavelet analysis to examine spatiotemporal rainfall variability and the influence of major ocean-atmosphere circulation patterns, including Niño-4, North Atlantic Oscillation (NAO), Southern Oscillation Index (SOI), and Mediterranean Oscillation Index (MOI). The SPI values indicate year-to-year variability ranging from 3.2 (extremely wet) to -2 (severe drought). Wavelet analysis reveals short- and long-term rainfall periodicities of 2–3, 3–5, and 6–10 years, which correspond to similar cycles in oceanic indices (2–3, 3–5, 6–10, and 8–13 years). Results highlight significant teleconnections between oceanic fluctuations and rainfall anomalies in different parts of Ethiopia. For instance, the northern region experienced a wet event (2.5 SPI) around 2001, influenced by Niño-4 (1992–2003); the southern region faced severe drought (-2 SPI) in 2014/2015, linked to NAO (2009–2016); and the western region was affected by SOI during 1992–2005, with droughts in 1994/1995 and 2003. The findings emphasize the role of oceanic anomalies in driving regional precipitation variability, providing valuable insights for water resource management and climate adaptation strategies. This study also bridges gaps in previous research by employing wavelet analysis to uncover time-frequency dynamics, particularly for SOI and MOI, offering a deeper understanding of precipitation teleconnections in Ethiopia.