Submesoscale velocity gradients observed by Saildrones

Cesar B Rocha, Woods Hole Oceanographic Institution, Woods Hole, MA, United States, J. Thomas Farrar, Woods Hole Oceanographic Inst, Department of Physical Oceanography, Woods Hole, United States, Andrey Shcherbina, Applied Physics Laboratory University of Washington, Seattle, WA, United States, Eric A. D'Asaro, Applied Physics Laboratory University of Washington, Seattle, United States and H. Hawkeye King, Saildrone Inc., Alameda, United States
Saildrones are wind-and-solar-powered unmanned surface vehicles rigged with atmospheric and oceanic sensors. In Spring 2019, an array of three Saildrones were deployed at the Golden Gate Bridge and sailed parallel tracks into the California Current region, crossing fronts and filaments. These saildrones were equipped with 300 kHz Teledyne Workhorse Monitor ADCPs mounted on their keels. A careful analysis of the ADCP error budget reveals that the velocity accuracy is 2 cm/s for 5-minute averages, with a horizontal resolution of about 600 m. Thus, saildrone-mounted ADCPs allow for accurate estimation of kilometer-scale velocity gradients. We will discuss a detailed application of these velocity-gradient estimates, together with near-surface density observations, to characterizing submesoscale individual features and statistics in the California Current region.