Details of Award
NERC Reference : NE/N008448/1
Air-sea exchanges at the ocean mesoscale: a driver of the ocean circulation?
Training Grant Award
- Lead Supervisor:
- Dr D Ferreira, University of Reading, Meteorology
- Grant held at:
- University of Reading, Meteorology
- Science Area:
- Atmospheric
- Marine
- Overall Classification:
- Marine
- ENRIs:
- Global Change
- Science Topics:
- Boundary Layer Meteorology
- Ocean - Atmosphere Interact.
- Tropospheric Processes
- Ocean - Atmosphere Interact.
- Ocean Circulation
- Abstract:
- Throughout the globe, the ocean and the atmosphere exchange massive amounts of energy and water that couple the evolutions of the two circulations together. Winds blowing over the oceans are the main mechanism for setting the oceans in motion. These winds also control the evaporation out of the ocean that replenishes the water content of the atmosphere, compensating for rain. In the same process, the energy released by the condensation of water vapor into raindrops powers the atmospheric flow. Because air-sea interactions are such a fundamental process, forecasting systems (eg. those employed at the Met Office) increasingly rely on coupled ocean-atmosphere numerical tools for seasonal, and soon for short-range, weather forecasts. Air-sea exchanges vary in space and time. With the increasing quality of satellite observations, it has become apparent that intense air-sea exchanges occur on the scales set by the oceanic turbulence. The global ocean is full of eddies, or vortices, generated by the instability of ocean currents. These eddies are relatively small, typically 50-100 km wide -- much less than the scale of oceanic basins (1000's km). Observational evidence shows that air-sea exchanges are modified by the presence of ocean eddies. This is because eddies tend to enclose warmer or colder waters than the surrounding ocean. The eddy temperature signal enhances or subdues mixing in the atmospheric surface layer, which in turns modifies the surface wind blowing over the oceans. For example, warm core eddies are associated with a more intense turbulent mixing and stronger surface winds. Through this mechanism, the ocean imprints its turbulent structure onto the global marine Atmospheric Boundary Layer (ABL) and generates a rich atmospheric variability on scales of 100's km. Air-sea interactions over ocean eddies are a new frontier in our understanding of the coupled system, contrasting with the basin-scale interactions that have been extensively investigated. Studies of the air-sea exchanges over ocean eddies have been concerned with effects on surface winds and impacts on the atmospheric circulation. This project will explore the oceanic aspects, which have received comparatively less attention. The new high-resolution coupled simulation (ORCA012/N512) developed at the Met Office offers a fantastic opportunity to investigate this topic. Preliminary analysis showed that the new simulation captures the temperature-wind relationship with the observed intensity, providing a solid basis to explore new ground. The main goals are to understand and to quantify the impact of the eddy-ABL interaction on the ocean state: is it a fundamental mechanism that needs to be accounted for in the analysis and design of climate models? The PhD project is organized around three sub-themes: - Quantify the effect of oceanic eddies on air-sea fluxes of heat and moisture: The effect on winds (momentum fluxes) has been well evaluated but other components must be considered before exploring the impact on the ocean circulation. This will be carried out through an analysis of the ORCA012/N512 Met Office simulation. - Clarify the mechanisms and quantify the impact on the ocean circulation. To this end, the student will first use idealized NEMO configurations (channel, double-gyre) and then a realistic eddy-permitting configuration. Impact of momentum fluxes (on e.g. the mean circulation, frontal structures) will be contrasted with that of buoyancy fluxes (e.g. water mass transformation). - Represent the Eddy-ABL interaction in models where it is absent. This is the case in coarse climate models (eddies are not resolved) and in high-resolution ocean-only models (atmospheric fields are prescribed independently of the simulated eddies, e.g. CORE2). Building on the outcomes of 1) and 2), the student will design a parameterization of the Eddy-ABL interaction for coarse resolutions to be evaluated against high-resolution simulations.
- NERC Reference:
- NE/N008448/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Industrial CASE
This training grant award has a total value of £96,649
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - RTSG | Total - Student Stipend |
|---|---|---|
| £19,052 | £11,000 | £66,599 |
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