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The development of autonomous surface vehicles, such as the Boeing Liquid Robotics Wave Glider, has revolutionized our ability to collect surface ocean–lower atmosphere observations, a crucial step toward developing better physical understanding of upper-ocean and air–sea interaction processes. However, due to the wave-following nature of these vehicles, they experience rapid shifting, rolling, and pitching under the action of surface waves, making motion compensation of observations of ocean currents particularly challenging. We present an evaluation of the accuracy of Wave Glider–based ADCP measurements by comparing them with coincident and collocated observations collected from a bottom-mounted ADCP over the course of a week-long experiment. A novel motion compensation method, tailored to wave-following surface vehicles, is presented and compared with standard approaches. We show that the use of an additional position and attitude sensor (GPS/IMU) significantly improves the accuracy of the observed currents. [ABSTRACT FROM AUTHOR]

Surface waves play an important role in the ocean–atmosphere coupled climate system by mediating the exchange of momentum, heat, and gas between the atmosphere and the ocean. Pseudo-Lagrangian autonomous platforms (e.g., Boeing Liquid Robotics Wave Gliders) have been used to investigate the underlying physical dynamics involved in these processes to better parameterize the air–sea exchange occurring at the scale of the surface waves. This requires accurate measurements of directional surface waves down to short scales [O(1) m], as these shorter waves support most of the stress between the atmosphere and the ocean. A challenge to overcome for pseudo-Lagrangian autonomous vehicles is that the platform's velocity causes the observed frequency of the waves to be Doppler shifted. This leads to a modulation of the wave spectrum, particularly at high frequencies, that depends on the platform's speed, the wave frequency, and the relative angle between the direction of wave and platform propagation. In this work, we propose a method to account for Doppler effects that considers the full directionality of the wave field. The method is validated using a unique dataset collected from a fleet of two Wave Gliders off the coast of Southern California in September 2019 operating on the perimeter of a tight square (500-m edge length) track over a 3-day deployment. This technique can be used to estimate wave spectra derived from other slow-moving surface vehicles such as Saildrones that use platform motion to characterize the surface wave field. MATLAB routines to implement this method are publicly available. Significance Statement: The purpose of this study is to introduce a general approach that corrects observations of ocean surface waves collected on board autonomous surface vehicles (ASVs) for the effects on the wave period due to the vehicle's forward motion. This is important because improving climate models requires accurate measurements of short-wavelength waves, which can be readily obtained from ASVs. Our method provides the tools for ASVs to better understand air–sea physics and the larger role ocean surface waves play in Earth's climate system. [ABSTRACT FROM AUTHOR]

Measurements from the Campbell CSAT3 and Gill R3-50 anemometers were conducted in four different experiments, in laboratory and field environments. Consistent differences between these two sonic anemometers were observed. The data have revealed that the differences were strongly correlated with the wind direction. According to the datasets used, the CSAT3 was the anemometer whose measurements were more sensitive to the instrument's orientation relative to the wind direction. While the mean wind speed and direction remained within the manufacturers' specifications (a few percent for the wind speed and a few degrees for the wind direction), the estimates of the friction velocity from the CSAT3 differed from the R3-50 by up to 20%. [ABSTRACT FROM AUTHOR]