Two ’Bots Good: air-sea interaction with coordinated subs and drones

Supervisory team:

Dr Phil Anderson (SAMS-UHI)
Prof Mark Inall (SAMS-UHI)
Dr Matthew Palmer (NOC)
Dr Margaret Yelland (NOC)

Project Description:

The underlying physics of how heat, momentum, trace gases and aerosol precursors cross the air-sea boundary is still poorly understood. This is in part due to the complex nature of the mobile surface in all but calm conditions, but also due to the media of water and air being low viscosity fluids, invariably in turbulent motion. Traditionally, surface-process studies in oceanography and meteorology have moved in relatively separate theatres, and the sea surface itself is a grey area of unknown, treated by opposing communities with the simplest of physics. The advent of in situ turbulence sensors both on sub-surface AUVs and airborne UAVs is an opportunity to break through this disparate situation.

Recent exponential increase in interest in surfactant effects at sea, linked closely with the public’s demand for industry to have greater control over oil spill, offers a clear industry end user to Double Boundary Layer (DBL) studies, with immediate impact, contrasting with the longer term requirements of the coupled air-ocean climate modelling community. The final goal is to find vertical turbulent diffusivities in both the upper mixed layer of the ocean, and the lower surface layer of the atmosphere over a range boundary layer stability parameter space.

The project will initially have two themes, to develop separately AUV and UAV turbulent platforms suitable for deployment in real environments. These will be drawn together for a real field trial toward the end of the project, and the techniques passed on to, we suggest, multiple-sensor fleets able to measure the full spectrum of air ocean exchanges.

Turbulent transport of heat and momentum from the atmosphere into the surface can be measured directly using eddy covariance (EC) techniques. Recently, miniaturised micro, multi-hole pitot tube and accelerometer sensors have made UAV-based EC measurements a possibility (Martin et al. 2011). The Scottish Association for Marine Sciences (SAMS) will develop a marine version of this system.

Sub-sea turbulence sensors are now available for both AUV and gliders. This issue here will be assessing various methods of maintaining constant depth near the surface.

Finally the project will assess methods for making co-temporal, co-spatial measurements using the two robotic styles. The end goal will be spatially and temporally co-incident quantification of vertical turbulent fluxes in both marine and atmospheric boundary layers over a range of boundary layer stability regimes.  

The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for the environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at University of Highlands and Islands and hosted at Scottish Association for Marine Science (SAMS). Specific training will include:

• RPAS Pilot / ground control training
• Micro-meteorology (that is, environmental boundary layer turbulence)
• Oceanography
• Basics of Control theory and Avionics tuning

NB There is natural synergy between this Project and (a) Melt Pond Albedo and (b) Terrain Following UAVs. Training may be combined.

References

Martin, S., Bange, J., and Beyrich, F.: Meteorological profiling of the lower troposphere using the research UAV "M2AV Carolo", Atmos. Meas. Tech., 4, 705-716, doi:10.5194/amt-4-705-2011, 2011.