Coastal Meteorology A Review of the State of the Science (1992) / Chapter Skim
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2. Boundary Layer Processes
2. Boundary Layer Processes
Pages 9-18
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From page 9... ...
In fact, many common ABL conditions are still poorly understood even for homogeneous surfaces. The horizontally inhomogeneous and rapid temporal forcing conditions typical of coastal regions dictate consideration of problems that have rarely been investigated.
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From page 10... ...
Ensemble average models are often referred to as higher-order closure models. Grid-volume average models are usually referred to as large eddy simulation (LES)
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From page 11... ...
Compared to the ABL, the overlying free troposphere can be considered essentially nonturbulent. Surface layer similarity theory is based on scaling parameters obtained from the surface fluxes (Wyngaard, 1973~.
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From page 12... ...
Note the strong low-level inversion in potential temperature at approximately 250 m altitude, coincident with the maximum in wind speed. Contrast these profiles with the simple mixed layer structure depicted in Figure 2.1.
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From page 13... ...
In numerical models (or when the direct method is not available or applicable) , bulk transfer coefficients and surface layer similarity parameterizations are used to relate the fluxes to the near-surface mean meteorological variables and the surface properties.
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From page 14... ...
Fetch is primarily an issue for offshore wind conditions, but distortion of the open ocean directional wave spectrum in coastal shallow regions is important regardless of wind regime; it becomes increasingly important as wind speeds increase. Sounds and estuaries add complexities, often with irregular coastlines, river deltas, and islands.
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From page 15... ...
Substantial hydrostatic stability modulation of stress and surface wind fields has also been observed in association with sea surface temperature variations typical of coastal regions. A comprehensive theoretical and experimental study of wind-wavestress-scalar flux relationships on the continental shelves should be an important component of a coastal meteorology research program.
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From page 16... ...
The Inhomogeneous Atmospheric Boundary Layer Understanding ABL development and evolution in regions of abrupt or gradual changes of surface properties (coastal zones, ice-to-water surface transitions, ocean surface temperature fronts, etc.) involves consideration of horizontal advection, baroclinic forcing, nonequilibrium turbulence effects (for instance, the time derivative of the turbulent kinetic energy is not negligible)
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From page 17... ...
, "Most observational and model studies show that in the absence of abrupt changes in boundary conditions, the heat flux profile is indeed essentially linear in the mixed layer. Thus, given the proper boundary conditions, second-order models will tend to have the correct vertical profile of buoyant production rates within the mixed layer, regardless of the fidelity of their closure parameterizations." Moeng and Wyngaard also point out that under homogeneous conditions the mean value of the rate of dissipation of turbulent kinetic energy in the mixed layer is also nearly independent of closure approximations.
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From page 18... ...
· Investigations to clarify coastal marine stratocumulus and overland fair weather cumulus cloud regimes and their influence on land-sea breeze cycles should be conducted. · Studies should be undertaken to determine the spatial scale at which horizontal inhomogeneities in surface heating and cooling become large enough to generate coherent wind circulations.
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