Lake Breeze Circulation Research Articles

Observational evidence for the impact of the lake breeze circulation on ozone concentrations in Southern Ontario

Very rapid increases in the concentrations of ozone and ozone precursors, in the late afternoon, have been observed at a rural and an urban site in southern Ontario. Ozone concentration increases of 30 ppbv in a few minutes have been observed. These increases occur simultaneously with the arrival of a Lake Ontario lake breeze front as identified from meteorological measurements and visible satellite imagery. This indicates that polluted air masses from over Lake Ontario are being transported inland by the lake breeze. Aircraft measurements of ozone, NO x , and hydrocarbons show such an air mass moving inland. Chemical measurements at the sites show that the polluted air masses are not of local origin, but are of similar age to those regularly encountered in rural areas.

Numerical Modelling of the Effects of Vegetation and Environmental Conditions on the Lake Breeze

The influence of vegetation and environmental conditions on the lake breeze and associated boundary-layer turbulence structure has been studied using a two-dimensional nonhydrostatic, compressible mesoscale model coupled with the SiB2 land-surface scheme. The results show that the impacts of vegetation on the lake effects are dependent on the environmental conditions, such as soil wetness and background wind, as well as vegetation characteristics. Both soil wetness and background wind play important roles in modifying lake effects on boundary-layer turbulence and the lake breeze, while the effects of vegetation type are secondary compared to the other factors. Without background wind, and under the same soil wetness, the maximum horizontal windspeed of the lake breeze is insensitive to the type of vegetation. Soil wetness can greatly affect both the maximum horizontal windspeed and the maximum vertical velocities of the lake breeze. With background wind, the lake-breeze circulations, upward motion regions, and boundary-layer turbulence structure all change markedly. A weaker background wind can strengthen the lake breeze, while stronger background wind suppresses the lake breeze circulations. The distribution of sensible and latent heat fluxes is also very sensitive to the soil wetness and background wind. However, for the same soil wetness (0.25 and 0.4 were chosen), there is only a small difference in the distribution of sensible and latent heat fluxes between the bare soil and vegetated soil or between the types of vegetated soils.

Lake‐induced atmospheric circulations during BOREAS

Lake‐induced atmospheric circulations over three lakes ranging from 3 to 10 km width are analyzed using data from three aircraft during the 1994 Boreal Ecosystem‐Atmosphere Study (BOREAS). A well‐defined divergent lake breeze circulation is observed over all three lakes during the day. Under light wind conditions, the lake breeze is not very sensitive to the water temperature, and the strength of the divergence over the lake decreases with increasing lake size. The boundary‐layer development over the surrounding land can be very important for generating a horizontal pressure difference which drives the lake breeze. Diurnal and seasonal variations of lake breezes are investigated on the basis of repeated passes from the different aircraft at different altitudes from late spring to early fall of 1994. The lake breeze divergence increases with time during the day and reaches a maximum around 1300 LST. The latent heat flux over 10‐km‐wide Candle Lake increases steadily from spring to fall as the lake temperature increases. The latent heat flux over the land reaches a maximum during the summer due to evapotranspiration. The lake effect on area‐averaged fluxes sometimes leads to a negative heat transfer coefficient for an averaging scale of several times the lake width.

Lake/Land Breeze Circulations on the Western Shore of Lake Michigan

Abstract A classic lake breeze circulation cell that formed on the western shore of Lake Michigan on 4 September 1974 is studied in great detail. Wind measurements are made with surface anemometers and serial pibals, with air trajectories monitored via tetroons. Aircraft measurements map the thermal internal boundary layer and small and large aerosol distributions. Recirculation of pollutants is indicated from analysis of the tetroon data. Aerosol measurements suggest size sorting of small versus large particles as they are transported through the complex three-dimensional flow. These wind data also form the basis of a kinematic diagnostic study of mesoscale pollution transport in coastal areas, to be reported in a subsequent paper.

A Lake Breeze over Southern Lake Ontario

This paper describes a combined observational and theoretical study of a lake breeze over the southern shore of Lake Ontario on 3 October 1972. The structure of the lake breeze circulation and its variations in time were obtained from observations. The observational data were gathered with a specially designed array of surface stations, tethered balloons, pilot balloons, aircraft and buoys. A two-dimensional, time dependent, primitive equation model was constructed to simulate the observed lake breeze. The numerical simulation is reasonably realistic; however, the lake breeze intensity and Wand penetration were under-estimated.

Detailed Mesometeorological Studies of Air Pollution Dispersion in the Chicago Lake Breeze1

Abstract The lake-breeze circulation on the Great Lakes is often as vigorous as its oceanic counterpart. This paper shows that lake breezes frequently exert drastic control on mesoscale air pollution patterns in urbanized shore-line areas, in this case, Chicago, Ill. Observational data were gathered from a surface mesonetwork, surface and satellite cloud photography, a chain of pilot balloons normal to the shore, optically tracked constant-level balloons, and aircraft measurements of suspended particulate concentrations in several size ranges. On the 2 late summer days studied, the lake breezes were extremely well developed. Inflow depths ranged from 500 to 1000 m, with peak inflow velocities of 6–7 m/s. Beginning at the shore-line between 0800 and 0900 LST, the breezes penetrated inland over 40 km. Clearly defined return flow layers were present both days. Eulerian wind field measurements from serial pilot, balloon releases were used to make cross sections of the u wind component. Computed one-dimensiona...

Fumigation and Plume Trapping on the Shores of Lake Michigan During Stable Onshore Flow

Abstract Previous studies have shown that the lake breeze circulation cell which develops along the western shore of Lake Michigan during almost half of the warm season days has detrimental effects upon the air quality of the Gray-Chicago-Milwaukee area. However, stable onshore flow associated with a synoptic-scale pressure gradient occurs for an additional 15% of warm season days. This study examines the dispersion patterns during gradient, onshore flow. Fumigation and plume trapping, in particular, appear to cause serious degradation of air quality. Continuous fumigation of elevated plumes develops on days with strong insulation. Plume trapping occurs when a plume is emitted into a shallow layer of unstable air capped by a deep lid of stable air. This condition is frequent on overcast spring days. Two days characterized by easterly gradient winds were studied: 27 May 1970, overcast; 25 June 1970, predominately sunny. The studies utilized meteorological data obtained from ground observers, ship's records...

Lake effects on air pollution dispersion.

Local wind regimes induced by a lake or a shoreline may have a major influence on air pollution dispersion. Pressure differences due to differential heating of the air, e.g., that due to differences in surface characteristics, are the driving forces of lake and land breeze circulations and slope and valley winds. Differences in roughness between land and lake surfaces will cause wind shear and aerodynamic downwash effects at a shoreline. Stability changes in the air result from differences in surface temperature and roughness between land and lake, e.g., when warm unstable air moves out over a cool lake a temperature inversion will develop near the surface giving very poor dispersion conditions in this lower layer. Pollution released in this stable layer may be carried in high concentrations for many miles and cause severe damage as the air moves across a down wind shoreline and advances inland. The information presented is designed to permit an assessment of the probable complexity of the dispersion patt...