Characterizing the swell-dominated wave climate off West Africa: an intercomparison of global wave reanalyses

• WAVERYS outperforms ERA5 due to higher resolution and current effects on waves • 99% significant wave heights off West Africa exhibit increasing trend up to 1.0%/yr • Waves peak during boreal winter/summer in the North/South Atlantic off West Africa This study investigates wave climate off West Africa using 35 years (1990–2024) of ERA5 (0.5° resolution) and WAVERYS (0.2° resolution) global wave reanalyses. Validation against eight observational stations confirms WAVERYS' superior performance in predicting significant wave heights (SWHs) and peak wave periods, due to its higher resolution and advanced physics incorporating current effects. The intercomparison reveals WAVERYS generates stronger swells (+10%) and weaker wind waves ( − 20%) than ERA5, expanding the swell-dominated zone. Annual mean SWHs off West Africa exhibit notable spatial variability, characterized by a pronounced meridional gradient decreasing from ∼2.5 m in the subtropics to ∼1.5 m near the equator. Wave periods and directions show a distinct north-south divide that longer southerly swells dominate the South Atlantic, while relatively shorter northerly waves prevail north of 10°N. The annual mean 99% SWHs from WAVERYS decrease from ∼9.0 m in the subtropical oceans to ∼3.0 m equatorward, with an increasing trend by up to ∼1.0%/year across the domain. ERA5 captures similar spatial patterns of extreme waves but with significantly weaker magnitudes and trend intensity. Moreover, waves exhibit significant seasonality that mean and extreme SWHs peak during boreal winter in the North Atlantic but during boreal summer in the South Atlantic. This work highlights importance of advanced model resolution and physics for accurately quantifying wave climate.