APL-UW Home

Jobs
About
Campus Map
Contact
Privacy
Intranet

Ramsey Harcourt

Principal Oceanographer

Email

harcourt@apl.washington.edu

Phone

206-221-4662

Research Interests

Large Eddy Simulation (LES), Computational Fluid Dynamics, Deep Convection, Wave and Ice Boundary Layers, Response of Drifters to Convection

Department Affiliation

Ocean Physics

Education

B.S. Physics, Reed College, 1987

M.S. Physics, University of California - Santa Cruz, 1989

Ph.D. Physics, University of California - Santa Cruz, 1999

Publications

2000-present and while at APL-UW

Suppression of CO2 outgassing by gas bubbles under a hurricane

Liang, J.-H., E.A. D'Asaro, C.L. McNeil, Y. Fan, R.R. Harcourt, S.R. Emerson, B. Yang, and P.P. Sullivan, "Suppression of CO2 outgassing by gas bubbles under a hurricane," Geophys. Res. Lett., 47, doi:10.1029/2020GL090249, 2020.

More Info

28 Sep 2020

The role of gas bubbles on the air‐sea CO2 flux during Hurricane Frances (2004) is studied using a large‐eddy simulation model that couples ocean surface boundary layer turbulence, gas bubbles, and dissolved gases. In the subtropical surface ocean where gases are slightly supersaturated, gases in bubbles can still dissolve due to hydrostatic pressure and surface tension exerted on bubbles. Under the simulated conditions, the CO2 efflux with an explicit bubble effect is less than 2% of that calculated using a gas flux formula without explicit inclusion of bubble effect. The use of a gas flux parameterization without bubble‐induced supersaturation contributes to uncertainty in the global carbon budget. The results highlight the importance of bubbles under high winds even for soluble gases such as CO2 and demonstrate that gas flux parameterization derived from gases of certain solubility may not be accurate for gases of very different solubility.

Advances in observing and understanding small-scale open ocean circulation during the Gulf of Mexico Research Initiative era

D'Asaro, E.A., D.F. Carlson, M. Chamecki, R.R. Harcourt, B.K. Haus, B. Fox-Kemper, M.J. Molemaker, A.C. Poje, and D. Yang, "Advances in observing and understanding small-scale open ocean circulation during the Gulf of Mexico Research Initiative era," Front. Mar. Sci., 7, doi:10.3389/fmars.2020.00349, 2020.

More Info

20 May 2020

Predicting the distribution of oil, buoyant plastics, flotsam, and marine organisms near the ocean surface remains a fundamental problem of practical importance. This manuscript synthesizes progress in this area during the time of the Gulf of Mexico Research Initiative (GoMRI; 2012–2019), with an emphasis on the accumulation of floating material into highly concentrated streaks on horizontal scales of meters to 10's of kilometers. Prior to the GoMRI period, two new paradigms emerged: the importance of submesoscale frontal dynamics on the larger scales and of surface-wave-driven Langmuir turbulence on the smaller scales, with a broad transition occurring near 100 m. Rapid progress resulted from the combination of high resolution numerical modeling tools, mostly developed before GoMRI, and new observational techniques developed during GoMRI. Massive deployments of inexpensive and biodegradable satellite-tracked surface drifters combined with aerial tracking of oil surrogates (drift cards) enabled simultaneous observations of surface ocean velocities and dispersion over scales of 10 m to 10's of kilometers. Surface current maps produced by ship-mounted radar and aerial optical remote sensing systems, combined with traditional oceanographic tools, enabled a set of coordinated measurement programs that supported and expanded the new paradigms. Submesoscale fronts caused floating material to both accumulate at fronts and to disperse as they evolved, leading to higher local concentrations, but increased overall dispersion. Analyses confirmed the distinct submesoscale dynamics of this process and the complexity of the resulting fields. Existing tools could be developed into predictive models of submesoscale statistics, but prediction of individual submesoscale features will likely remain limited by data. Away from fronts, measured rates of accumulation of material in and beneath surface windrows was found to be consistent with Langmuir turbulence, but highly dependent on the rise rate of the material and thus, for oil, on the droplet size. Models of this process were developed and tested and could be further developed into predictive tools. Both the submesoscale and Langmuir processes are sensitive to coupling with surface waves and air-sea flux processes. This sensitivity is a promising area for future studies.

Small-scale dispersion in the presence of Langmuir circulation

Chang, H., and 12 others including R.R. Harcourt, "Small-scale dispersion in the presence of Langmuir circulation," J. Phys. Oceanogr., 49, 3069-3085, doi:10.1175/JPO-D-19-0107.1, 2019.

More Info

1 Dec 2019

We present an analysis of ocean surface dispersion characteristics, on 1–100 m scales, obtained by optically tracking a release of O (600) bamboo plates for 2 hours in the Northern Gulf of Mexico. Under sustained 5–6 m/s winds, energetic Langmuir cells are clearly delineated in the spatially dense plate observations. Within 10 minutes of release, the plates collect in windrows with 15 m spacing aligned with the wind. Windrow spacing grows, through windrow merger, to 40 m after 20 minutes and then expands at a slower rate to 50 m. The presence of Langmuir cells produces strong horizontal anisotropy and scale dependence in all surface dispersion statistics computed from the plate observations. Relative dispersion in the crosswind direction initially dominates but eventually saturates, while downwind dispersion exhibits continual growth consistent with contributions from both turbulent fluctuations and organized mean shear. Longitudinal velocity differences in the crosswind direction indicate mean convergence at scales below the Langmuir cell diameter and mean divergence at larger scales. Although the second order structure function measured by contemporaneous GPS-tracked surfacedrifters drogued at ~0.5 m shows persistent r2/3 power law scaling down to 100–200 m separation scales, the second-order structure function for the very near surface plates observations has considerably higher energy and significantly shallower slope at scales below 100 m. This is consistent with contemporaneous data from undrogued surface drifters and previously published model results indicating shallowing spectra in the presence of direct windwave forcing mechanisms.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
Close

 

Close