Presenter: Edward Cokelet (NOAA Pacific Marine Environmental Laboratory)

Description:
During July–November of the 2021 Atlantic hurricane season, five experimental saildrone USVs (uncrewed surface vehicles) with hurricane wings were deployed in the subtropical and tropical Atlantic Ocean to measure near-surface atmospheric and oceanographic properties near and ideally inside hurricanes. The saildrones measured solar irradiance, barometric pressure, air temperature, humidity, wind, waves, surface water temperature, salinity, chlorophyll, dissolved oxygen, and ocean current profiles. Two of the saildrones also measured surface short- and long-wave radiation. Vehicle positions and observations were transmitted and tracked in realtime. Where possible, saildrones briefly circled NOAA National Data Buoy Center buoys and rendezvoused with underwater gliders to obtain collocated and simultaneous observations of atmosphere and sea water properties in the upper 800 m of the ocean.  The saildrones encountered Tropical Storms Fred and Grace and Hurricanes Henri and Sam.  Category 4 Hurricane Sam was the strongest and is emphasized in the presentation.  Sam became a hurricane on 24 September, and passed 21 nm southwest of saildrone SD-1045 on 30 September 2021 15:00.  SD-1045 measured a minimum barometric pressure of  970 hPa, maximum sustained winds of 79 kt, gusts to 110 kt and a maximum significant wave height of 14 m.  On-board cameras recorded the chaotic sea state.  Sam grazed NDBC buoy 41044 90 nm away, providing valuable corroborating measurements.  Completed mission goals included (1) first USV measurements inside a hurricane, (2) successful deployment and recovery of five saildrones, (3) rendezvous with ocean gliders in five regions, (4) aircraft overflights, (5) realtime data transmission via GTS, and (6) first wave spectral measurements from a saildrone.