Spatial Association of Extreme Precipitation and Wave Climate Trends Along Coastal Zones of American Mediterranean Sea

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Extreme precipitation and waves both drive coastal hazards along the American Mediterranean Sea, yet whether the two have changed in coordinated ways over recent decades remains unclear. We analyzed 43 years (1981–2023) of coastal precipitation and wave climate across five sub-regions, using CHIRPS v2.0 daily rainfall at 2656 coastal land pixels and ERA5 wave reanalysis at 1159 nearshore ocean pixels. Five ETCCDI precipitation indices and five wave metrics were computed; their trends were estimated with the Mann–Kendall test and Sen’s slope, and their uncertainty was quantified by bootstrap resampling. Coastal precipitation shows a “fewer but more intense” pattern in parts of the basin: along the Mexican Gulf and Central American coasts, heavy-precipitation frequency (R10mm) declines by about 1.4 to 2.6 days/decade while the most extreme events intensify, with one-day maxima rising by about 6 mm/decade and five-day maxima by 7 to 10 mm/decade; trends in annual total precipitation are comparatively uncertain. Wave trends are generally positive, with significant wave height rising most rapidly off Central America (about 0.021 to 0.027 m/decade) and peak wave period lengthening most along the South American Caribbean coast. To test whether these changes are spatially linked, we paired neighboring land and ocean pixels and applied pairwise trend correlations, sub-regional time-series analysis, and joint clustering. Across the basin, coastal segments with stronger increases in extreme rainfall tend to coincide with segments of rising wave height. Among the examined index pairs, the largest positive correlation was observed between the trends in short-duration precipitation extremes (Rx1day and Rx5day) and the 90th-percentile wave height, although the association was modest (ρ≈0.28). Joint clustering suggests that concurrent positive trends are more frequently represented along the southwestern Gulf of Mexico and the Caribbean coast of Central America. These results indicate that the principal drivers of compound coastal flooding may not be evolving independently across this basin, and they support considering precipitation and wave climate change jointly in regional coastal hazard assessment.

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