UAS-Based Remote Sensing of the Upper Ocean Turbulence Response to Atmospheric Forcing
Abstract
The motivation of this work is to develop a new methodology enabling better understanding of the upper ocean response to the atmospheric forcing induced by momentum and heat fluxes across the air-sea interface. Offshore, the conventional approach has been to employ a research vessel equipped with meteorological instrumentation to resolve atmospheric conditions and with oceanographic profilers to resolve vertical structure of the upper ocean. The shortcoming of this approach, however, is that it resolves the time series at what is essentially one point on the air-sea interface and the vertical profile below it, leaving no other option but to assume spatially quasi-homogeneous submesoscale conditions around the study area. Both satellite and airborne ocean remote sensing were able to mitigate the lack of the spatial coverage to some degree, however, significant gaps in spatial, temporal and on-demand resolutions remain an issue. To provide more targeted spatial observations, in this study an unmanned aerial system (UAS) was launched and recovered from a research vessel, and was generally considered to be an additional tool available to the research vessel for the purposes of a larger air-sea interaction and upper ocean turbulence survey. The specific task performed by the UAS was to map plumes formed by streaks of a water tracing dye (Uranine) released from the research vessel. Multiple mapping flights over the dye resolved the evolution of the plume's shape in time, as it was getting entrained by turbulent structures on the spatial scales from 10s of meters to kilometers. During a 21 day long cruise, the total of 9 dye plumes were released and each surveyed with 3 to 5 consecutive UAS flights. The analysis of dye plume imagery allows detecting submesoscale features, such eddies or fronts, and also to estimate turbulent kinetic energy and dispersion on a wide range of length scales. Simultaneously with the UAS, the research vessel surveyed dye plumes with a fluorometer mounted on a vertically oscillating scanfish towed behind the vessel, thus obtaining the third (vertical) dimension of the 3D dye plume structure. Combined, these dye enabled observations of the upper ocean turbulence provided a unique and much needed addition to a suite of upper ocean turbulence observations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A41N3192S
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSESDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSES