Effects of the Large-Scale Flow on Characteristic Features of the Sea Breeze

Raymond W. Arritt Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas

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Abstract

A two-dimensional nonlinear numerical model has been used to examine the effects of the ambient wind on the development of characteristic features of the sea breeze. The specific features that were examined were the maximum shoreward velocity component (both total and as a perturbation from the large-scale flow) anywhere in the simulation domain, the inland penetration of the sea breeze, the depth of the inflow layer at the coastline, the maximum vertical velocity anywhere in the domain, the maximum potential-temperature gradient anywhere in the domain, and the surface heat flux. Thirty-one simulators were performed, with large-scale geostrophic winds ranging from onshore (i.e., supporting) flow of 15 m s−1 to offshore (i.e., opposing) flow of 15 m s−1, at 1 m s−1 intervals.

The results indicated that the sea-breeze perturbation was suppressed for onshore large-scale flow of a few meters per second or more. In contrast, a sea breeze was produced for opposing large-scale flow as strong as 11 m s−1. The sea-breeze cell was located offshore for strong opposing flow, with the sea-breeze velocities (both horizontal and vertical) being weaker than when the sea breeze penetrated inland. Both the stable stratification over the water and the convergence term in the froutogenesis equation are important factors in the sensitivity of the sea breeze to the large-scale flow.

Abstract

A two-dimensional nonlinear numerical model has been used to examine the effects of the ambient wind on the development of characteristic features of the sea breeze. The specific features that were examined were the maximum shoreward velocity component (both total and as a perturbation from the large-scale flow) anywhere in the simulation domain, the inland penetration of the sea breeze, the depth of the inflow layer at the coastline, the maximum vertical velocity anywhere in the domain, the maximum potential-temperature gradient anywhere in the domain, and the surface heat flux. Thirty-one simulators were performed, with large-scale geostrophic winds ranging from onshore (i.e., supporting) flow of 15 m s−1 to offshore (i.e., opposing) flow of 15 m s−1, at 1 m s−1 intervals.

The results indicated that the sea-breeze perturbation was suppressed for onshore large-scale flow of a few meters per second or more. In contrast, a sea breeze was produced for opposing large-scale flow as strong as 11 m s−1. The sea-breeze cell was located offshore for strong opposing flow, with the sea-breeze velocities (both horizontal and vertical) being weaker than when the sea breeze penetrated inland. Both the stable stratification over the water and the convergence term in the froutogenesis equation are important factors in the sensitivity of the sea breeze to the large-scale flow.

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