Publication Date

2010-12-22

Availability

Open access

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Applied Marine Physics (Marine)

Date of Defense

November 2010

First Committee Member

Maria J. Olascoaga - Committee Member

Second Committee Member

Brain K. Haus - Committee Member

Third Committee Member

Wlliam M. Drennan - Mentor

Fourth Committee Member

Rana A. Fine - Outside Committee Member

Abstract

A study of the turbulent transfer of properties across the ocean surface and the dissipation of the energy transferred to the upper ocean is here presented. Two experiments were analyzed, both conducted during summer in the North Atlantic during phytoplankton blooms. The Marine Aerosol Production from marine sources (MAP) experiment, performed during summer of 2004, allowed for the calculation of the air-sea turbulent fluxes of momentum and humidity in high wind conditions. This analysis aims to improve the parameterization of air-sea turbulent fluxes, fundamental for coupled atmospheric-ocean models. In particular, there are very few previous calculations of the bulk coefficients for humidity fluxes over 18m/s, making the present work a fundamental contribution to the field. Wind speed and humidity fluctuations were measured with an eddy flux tower mounted on a vessel. The methods applied to calculate momentum and humidity flux were the eddy correlation or eddy covariance, the bulk, and the inertial dissipation method. Due to strong flow distortion effects derived from the instrumentation set up on board, the inertial dissipation method proved to be the more appropriate calculation for this experiment. On the oceanic side, the Labrador Sea experiment conducted in summer 2004, allowed for the study of the dissipation of energy within the upper surface layer (up till 2 m depth). This study is useful to improve the understanding of the relevant surface processes that should be included in the parameterization of the turbulent kinetic energy dissipation rates. The measurements were obtained with an Air-Sea Interaction Spar (ASIS) buoy, which includes a flux tower and several instruments installed along its underwater structure. In particular we analyzed data from a pulse-to-pulse coherent Doppler sonar, which allows the calculation of current velocity fluctuations at densely spaced bins. The analysis of turbulent kinetic eddy dissipation rates (TKEDR) in different wind regimes allowed us to confirm the need to include the wave effects together with the wind, as a fundamental factor to parameterize the TKEDR. Near surface TKEDRs were found to be enhanced above classical law-of-the-wall estimates at moderate to high wind speeds, and also to be independent of the wave phase, even at high winds. This is contrary to recent observations showing TKEDR beneath wave crests to be significantly enhanced over those beneath wave troughs, and helps resolve a recent controversy in the literature. In summary, new perspectives on the air-sea flux parameterizations are presented in this dissertation. They will ultimately provide insight for the numerical model community for coupled atmospheric ocean models.

Keywords

Ocean Surface Boundary Layer; In Situ Data; Doppler Radar; Flux Tower

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