RAINFALL AND WIND VARIABILITY IN BASSE, THE GAMBIA: TEMPORAL TRENDS, EXTREME EVENTS, AND INTER-VARIABLE RELATIONSHIPS (2000-2025)

Abstract

Empirical analyses that integrate rainfall and wind variability remain scarce in The Gambia, despite the country’s high climate sensitivity. This study examined temporal trends, seasonal variability, extreme events, and intervariable relationships between rainfall and near-surface wind speed in Basse, Upper River Region, The Gambia (2000–2025) using NASA POWER (MERRA-2) monthly reanalysis data. Mann–Kendall trend tests, Sen’s slope estimator, P90/P10 percentile thresholds, standardized anomaly index (SAI), and Spearman rank order correlation were applied to 312 monthly observations per variable. Annual rainfall exhibited a significant positive trend (+15.36 mm yr⁻¹; MK τ = +0.280, p = 0.047), consistent with Sahelian monsoon recovery, whereas wind speed showed no significant change (−0.005 m s⁻¹ yr⁻¹; p = 0.269), reflecting the stability of the Harmattan West African Monsoon (WAM) alternation. Extreme wet years clustered in 2020–2022 and extreme dry years in 2000–2002, confirming a bimodal hydrometeorological regime shift. A strong inverse relationship between annual rainfall and wind speed (Pearson r = −0.73; Spearman ρ = −0.66; p < 0.001) identified monsoon Harmattan antagonism as the dominant atmospheric driver, with June being the only month with significant monthly coupling (r = −0.655, p < 0.001). These findings provide evidence-based insights into climate adaptation, agricultural planning, and disaster risk reduction in the Sudano-Sahelian zone.