Date of Completion

6-28-2013

Embargo Period

6-28-2013

Keywords

air-sea interaction, wind-wave coupling, boundary layer

Major Advisor

James B. Edson

Associate Advisor

James O'Donnell

Associate Advisor

Thomas Torgersen

Associate Advisor

Christopher J. Zappa

Field of Study

Oceanography

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Wave field and atmospheric observations during the Southern Ocean Gas Exchange experiment 2008 were used to explore air-sea boundary layer dynamics. The closure of a momentum budget at the air-sea interface allows the selection and tuning of a wave growth parameter consistent with the observed conditions. An energy balance between the atmospheric energy input and the observed wind-wave spectral energy is posed based on the turbulent kinetic energy budget. The energy input is defined as the rate of work done by the wave-induced stress over the wind velocity profile. Wave induced perturbations on the airflow are modeled by an exponential decay function with a variable dimensional decay rate (A m-1). Wave-induced perturbations are incorporated into the atmospheric input term to account for the wind-wave coupling. The decay rate is tuned iteratively by minimizing the difference between the input and the wind-wave spectral energy. Under weaker forcing the model works within 40-45%. It is hypothesized, that this is due to long-wave modulation and an upward ocean–atmosphere momentum flux. Under stronger forcing (i.e. 0.4 < u* < 0.9 m s-1) results are within 10-20% predicting progressively slower decay rates (A ~ 0.5 ± 0.4 m-1). This suggests that longer waves support the wave-induced momentum flux, extending the depth of the wave boundary layer to an average height of 2 m inducing stronger perturbations on the airflow. Under weaker forcing the model suggests that wind and waves become uncoupled exhibiting a shallower wave boundary layer.

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