NUMERICAL MODELING OF THE EFFECTS OF VEGETATION AND ENVIRONMENTAL-CONDITIONS ON THE LAKE BREEZE

The influence of vegetation and environmental conditions on the lake b reeze and associated boundary-layer turbulence structure has been stud ied using a two-dimensional nonhydrostatic, compressible mesoscale mod el coupled with the SiB2 land-surface scheme. The results show that th e impacts of vegetation on the lake effects are dependent on the envir onmental 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 turbu lence and the lake breeze, while the effects of vegetation type are se condary compared to the other factors. Without background wind, and un der the same soil wetness, the maximum horizontal windspeed of the lak e breeze is insensitive to the type of vegetation. Soil wetness can gr eatly affect both the maximum horizontal windspeed and the maximum ver tical velocities of the lake breeze. With back ground wind, the lake-b reeze circulations, upward motion regions, and boundary-layer turbulen ce structure all change markedly. A weaker background wind can strengt hen the lake breeze, while stronger background wind suppresses the lak e breeze circulations. The distribution of sensible and latent heat fl uxes is also very sensitive to the soil wetness and background wind. H owever, 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 he at fluxes between the bare soil and vegetated soil or between the type s of vegetated soils.