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

Abstract

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.