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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

Evaluating Monin–Obukhov scaling in the unstable oceanic surface layer

Zheng, Z., R.R. Harcourt, and E.A. D'Asaro, "Evaluating Monin–Obukhov scaling in the unstable oceanic surface layer," J. Phys. Oceanogr., EOR, doi:10.1175/JPO-D-20-0201.1, 2020.

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22 Dec 2020

Monin–Obukhov Similarity Theory (MOST) provides important scaling laws for flow properties in the surface layer of the atmosphere and has contributed to most of our understanding of the near-surface turbulence. The prediction of near-surface vertical mixing in most operational ocean models is largely built upon this theory. However, the validity of MOST in the upper ocean is questionable due to the demonstrated importance of surface waves in the region. Here we examine the validity of MOST in the statically unstable oceanic surface layer, using data collected from two open ocean sites with different wave conditions. The observed vertical temperature gradients are found to be about half of those predicted by MOST. We hypothesize this is attributable to either the breaking of surface waves, or Langmuir turbulence generated by the wave-current interaction. Existing turbulence closure models for surface wave breaking and for Langmuir turbulence are simplified to test these two hypotheses. Although both models predict reduced temperature gradients, the simplified Langmuir turbulence model matches observations more closely, when appropriately tuned.

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.

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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.

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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.

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
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