A Brazilian Northeast Coast Wave Data Comparison: Radar vs Buoy

Wave buoys are well known by its accuracy in measuring sea surface elevations while wave radars were developed later. Buoy’s motions are considered direct wave measurements while microwave radars use remote sensing for tracking the sea surface. Due to sensitivity to winds, sea surface roughness, rain, etc, it is a good practice to check radar data against buoys records. Even both systems installed being 6 km apart in a deep water region offshore northeast Brazilian shelf, there were differences in wave directional spectral parameters calculated by both equipments. The wave measurements at Sergipe and Alagoas basin were in good agreement in terms of significant wave height. Hs correlation was 91% and bias was only 0.06 m. A particular behavior of radar Hs when compared to buoy Hs was overestimation in high sea states and underestimation in low ones. Tp1 correlation was 69%, bias was 0.02 s and linear regression coefficient was 0.64. The worst correlated parameter was peak direction Dp1 with 60% of correlation for E-ESE directional band. Time series matched each other and showed the typical regional wave climate with Hs 1.0–2.0 m, Tp 6–10 s and Dp1 from E-ESE. The distinction between radar and the buoy directions is related to radar susceptibility to SE trade winds during Spring and Summer seasons. However, the difference did not diverge from prevailing wave regional climate.