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Title: On the coupling of air and sea

Date: 4:00 PM Wednesday, 7th November 2012
Venue: ATC 205, ATC building
Speaker: Prof Mark A. Donelan, Uni of Miami
Abstract: Air and sea are coupled through specification of the fluxes of momentum, heat and mass across their common boundary the air-sea interface.

The waves on the interface accept some of the momentum from the wind and release a part to the underlying currents. The amounts transferred to and released by the waves depend on the wave directional spectrum and its relationship with the boundary layer winds. Consequently, momentum and kinetic energy coupling cannot be accomplished without a wave prediction model acting as "the middle man".

The fluxes of heat and mass are controlled by the diffusive sublayers O(mm) on both sides of the interface and are therefore dependent on Schmidt number as well as roughness Reynolds number. The fluxes of gases of low solubility in water are also enhanced by disruption of the aqueous diffusive sublayer by wave breaking.

Bulk coefficients - drag coefficient, Stanton number, Dalton number and CO2 transfer coefficient - are used to relate these coupling fluxes to mean variables in the boundary layers. Attempts, by the author and colleagues to establish these coefficients over a wide range of wind speeds, are described. Field and tank measurements coupled with numerical models of waves and boundary layers lead to a generalized prescription of bulk coupling coefficients in neutral boundary layers.
Biography: Mark Donelan graduated from McGill University with an Electrical Engineering degree in 1964. After 2 years in industry in Hamilton, Ontario, he entered graduate school at the University of British Columbia to acquire a Ph.D. (physics) in 1970.

There followed a year's post-doctoral Killam fellowship in the Department of Applied Mathematics and Theoretical Physics, Cambridge University. He then joined the Canada Centre for Inland Waters, Burlington, Ontario, where for 25 years he pursued field, laboratory and modeling studies of waves and air-water interaction. In 1984 he was a Humboldt fellow at the Max-Planck Institut fur Meteorologie in Hamburg.

In 1996 he transferred to the University of Miami as Professor in Applied Marine Physics. He retired at the end of 2009 and is now Professor Emeritus at UM, working from his house on Vancouver Island. Along the way he was elected a fellow of the American Meteorological Society (1989) and of the Royal Society of Canada (1997).

He was awarded the Sverdrup Gold Medal of the American Meteorological Society in 1994.
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