Turbulent Diffusion and Pollutant Transport in Shoreline Environments

A parabolic shaped Thermal Internal Boundary Layer (TIBL) develops at the coast because of the temperature discontinuity between land and water. The TIBL is shown to play a significant role in determining where a coastal elevated plume fumigates to the ground. Six TIBL models available in the literature were identified and statistically compared. Two data bases obtained from the TIBL experiments, one at eastern Long Island, the other at the Kashimaura area ofJapan, were used for statistical comparisons. Statistical methods oft, F and R were used to determine bias, scatter and correlation. The data were also classified according to wind speed (low and high) and stability (unstable, neutral, isothermal and stable onshore flow) to determine whether some models worked better under certain conditions. These limited data indicated that a formulation which included heat flux and wind speed together with overwater lapse rate, all raised to the halfpower, performed the best. Classifications according to wind speed and thermal stability also showed that the heat flux type of equation worked reasonably well.

Section: Tibl Dynamicsmentioning

confidence: 99%

A comparative evaluation of the coastal internal boundary-layer height equations

Stunder

Sethuraman

1985

“…When air flows from offshore to onshore, it is modtied by changes in roughness, which produce a mechanical internal boundary layer (see, e.g., SethuRaman and Raynor, 1980), and/or by temperature contrasts, which produce a thermal or convective internal boundary layer (CIBL), as shown in Figure 1 (see, e.g., Lyons, 1975 studies related to the investigation of these internal boundary layers, particularly with respect to air pollution problems in coastal environments. Lists of these studies can be found in this journal (see, e.g., Ogawa and Ohara, 1985;Stunder and SethuRaman, 1985).…”

Section: Introductionmentioning

confidence: 99%

A note on estimating the height of the convective internal boundary layer near shore

Hsu

1986

When cool air flows from the sea over a warm coast, the air is thermally modified. It is shown that h = cX"a, where h is the height (in meters) of this thermal or convective internal boundary layer (CIBL) over the coast,Xis the distance downwind (in meters) from the shoreline (i.e., the fetch), and c is a coefficient that relates to the shear velocity and wind speed inside the CIBL, potential temperature difference and entrainment coefficient across the CIBL, and the lapse rate outside the CIBL. This equation is a simplification of a theoretical equation and is supported by three similar formulations based on thermodynamic and dimensional analyses. Pertinent field experiments conducted near shorelines in France, Sweden, and Japan indicate that c is approximately 1.91, with a standard deviation of 0.38. All observations are within 95% confidence limits.

“…This is especially true in complex coastal environments where a variety of phenomena including land-sea breezes, convergence zones and the development of thermal internal boundary layers may markedly complicate dispersion processes (Lyons, 1975;Hsu, 1988;Hanna, 1987). In standard dispersion modelling approaches, both the wind field and the PBL depth are frequently treated very simply.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of sea breezes over the Auckland region, New Zealand ? Air quality implications

McKendry

1989

The air pollution meteorology of a typical sea breeze day is investigated using the Colorado State University Mcsoscale Model. Results arc qualitatively compared with ohscrvations and revcal a complex wind field characterised by migratory sea breeze convergence zones. Associated with these features, the model predicts enhanced upward vertical velocities and 'doming' of the planetary houndary layer (PBL). The diurnal variation in PBL depth is shown to vary markedly at different locations and is dependent on position in relation to the migratory convergence zones. Thcsc complex spatial and temporal variations in the wind and PBL depth have important implications for air quality in Auckland and confirm that simple Gaussian or box trajectory approaches are inappropriate for air quality assessment in such environments. The inclusion in the model of variable surface properties, a dynamic synoptic state and improved PBL parameterisations. as well as coupling with a Lagrangian particle model, are recommended if the model is to he used as a tool for further air quality studies in the Auckland area.