Date of Award

Winter 2003

Project Type

Dissertation

Program or Major

Earth Sciences

Degree Name

Doctor of Philosophy

First Advisor

Barry Keim

Abstract

The synoptic and mesoscale environments conducive to the formation of sea breezes were examined, as well as the spatial and temporal evolution of sea-breeze circulations, gravity currents, and fronts along the central New England coast. Sea breeze events were defined as occurring when the observed surface wind direction began the day outside the southeast quadrant, shifted to southeast by afternoon, then shifted back out of the southeast quadrant in the evening, driven by mesoscale, insolation-induced cross-shore temperature gradients.

The meso-alpha (200--2000 km) sea-breeze forcing in the study area was defined as a combination of the cross-shore potential temperature gradient (deltatheta/deltax) that may drive sea breezes inland, and the cross-shore geostrophic wind component (uG) that may resist the landward movement of sea breezes. It was found that the peak values and temporal evolution of the meso-alpha forcing were dependent on the locations and relative dominance of synoptic-scale surface pressure systems in the eastern United States. These conclusions can often be used to accurately predict sea-breeze events, and their time of onset, using surface observations recorded in the early morning. The forecasting technique is adaptable to any coastal location in the world.

Meso-beta (20--200 km) horizontal variations in the sea-breeze circulation, gravity current, and front were compared to deltatheta/deltax and the cross-shore wind component at 925 hPa (u925) in the study area. The latter was substituted for uG because it also accounts for the synoptic-scale temperature gradient between the surface and 925 hPa via the thermal wind relation. Near-surface potential temperature (isentropic) fields were used to examine the sea-breeze gravity current, and the wind (kinematic) fields were used to examine the sea-breeze circulation. Isentropic gradient fields were used to examine the thermodynamic sea-breeze front, and convergence fields were used to examine the kinematic sea-breeze front. It was found that the most developed pattern the sea-breeze gravity current achieved, the time of the sea-breeze circulation's first contact with the coast and its most advanced inland distance, and the peak meso-beta strength of the sea-breeze frontal components were all functions of the meso-alpha forcing.

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