Saildrone: Unmanned Surface Vehicle for surface current and air-sea flux observation

Abstract:

Over the past decade, significant progress has been made in the global ocean observing system (GOOS), which is monitoring much of the upper ocean on a global scale in real time with multiple observing platforms. However, observation of air-sea fluxes has been relying on fixed surface moored buoys and research and voluntary ships with limited spatial coverage. As a result, the current GOOS is not able to adequately observe the air-sea interaction processes across fronts and eddies. A recent technology development, the saildrone, is an Unmanned Surface Vehicle (USV) powered by wind and solar energy with a range of more than 6,000 nautical miles, making it a potential platform to sample across fronts and weather systems over the global ocean. To make the saildrones capable of observing air-sea interaction processes, we have installed sensors with equivalent or better quality than those currently used on Tropical Atmosphere and Ocean (TAO) buoys for air-sea flux measurements, and a 300-kHz Acoustic Doppler Current Profiler for upper ocean current measurements. So far, three pilot Saildrone Missions have been completed in the tropical Pacific, as part of the Tropical Pacific Observing System (TPOS)-2020 project: one mission with two saildrones deployed and recovered from California; the other two deployed and recovered four saildrones from Honolulu, Hawaii. All missions reached the equator, sampled across the tropical Pacific cold tongue fronts and oceanic vortices and sent data in realtime to the GTS. We will present the saildrone data from these TPOS missions to evaluate the relationship of surface currents and air-sea fluxes, and use these results to demonstrate the importance of simultaneous measurements of ocean currents and air-sea state variables, and the potential of saildrones for air-sea interaction studies in the Tropical Pacific.