Can Saildrones Measure Directional Wave Spectra?

Saildrone's Uncrewed Surface Vehicle (USV), the Explorer, has been used to record basic non-directional measurements of ocean surface waves such as wave energy density, significant wave height, and dominant wave period. This investigation determines if the saildrone can accurately measure bulk wave measurements, as well as more detailed directional characteristics of waves such as directional wave spectra. Oceanographers desire accurate directional wave measurements from mobile platforms to understand and predict extreme conditions in the ocean and atmosphere such as hurricanes, where routine surface recordings of waves have been previously unavailable. This project developed a Python toolbox to identify, evaluate, and compare wave measurements collected from Saildrone USVs near moored buoys from NOAA's National Data Buoy Center (NDBC) and the Coastal Data Information Program (CDIP). Months worth of hourly datasets were collected from Saildrone missions across a range of calm seas to hurricanes with 50 foot waves. Statistical investigations found that the Saildrone USVs are able to reproduce bulk wave measurements and nondirectional spectra well in a wide range of regimes. However, more process oriented comparisons on directional wave measurements are recommended, especially in coastal regions where wave propagation is constrained by local topography, and the USVs and buoys were not exactly co-located.