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- Author or Editor: Jiang Weimei x
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Abstract
A 2D higher-order turbulence closure model for research on the structure of the thermal internal boundary layer (TIBL) has been developed in this paper. The mean quantities (temperature and wind), as well as their turbulent moments and their distribution under the TIBL, were computed. Results of numerical simulation show that under the initial condition of onshore flow and surface temperature on land being higher, than on water. 1) the profile of the TIBL on shore can be identified by the distributions of the mean wind and temperature, and during the integration hours there is an unstable stratified region over land that extends upward and inland gradually; 2) the shape of the profiles of the TIBL is roughly in concordance with observed profiles, but there are some differences, obviously, between the results computed by the formula of h ∼ x
1/2 and the results of the numerical experiment; and 3)
Abstract
A 2D higher-order turbulence closure model for research on the structure of the thermal internal boundary layer (TIBL) has been developed in this paper. The mean quantities (temperature and wind), as well as their turbulent moments and their distribution under the TIBL, were computed. Results of numerical simulation show that under the initial condition of onshore flow and surface temperature on land being higher, than on water. 1) the profile of the TIBL on shore can be identified by the distributions of the mean wind and temperature, and during the integration hours there is an unstable stratified region over land that extends upward and inland gradually; 2) the shape of the profiles of the TIBL is roughly in concordance with observed profiles, but there are some differences, obviously, between the results computed by the formula of h ∼ x
1/2 and the results of the numerical experiment; and 3)
Abstract
A forest canopy model is developed and coupled into the Regional Boundary Layer Model (RBLM) to fully consider the vertical structure of tree morphology. Instead of a slab surface model formerly used to represent trees in RBLM, the new version allows refinement of the radiation budgets as well as sensible and latent heat fluxes and, hence, more precise simulation of the thermal impacts of tree plantings on urban meteorological behavior. By applying this new version of RBLM, sensitivity tests are conducted to explore the potential impacts of different greenery scenarios on the thermal environment in an eastern Chinese city, Suzhou, during hot summer days. Greenings, both tree planting and grass surfacing, are beneficial in cooling the ambient air temperature. In general, tree planting is more beneficial than grass surfacing with the same coverage. In terms of surface energy balance, with tree coverage increasing from 0% to 20%, and then to 40%, the average surface net radiation fluxes at noon (1200 LST) are 591, 512, and 421 W m−2, respectively. Correspondingly, the Bowen ratio is reduced from 8.78 to 1.20 and then to 0.43 as result of the redistribution of solar energy absorbed at the ground. The cooling effect of trees is more significant at noontime and can remarkably lower the daily maximum air temperature in urban areas. The cooling effect of urban greenery increases with its coverage. Using the study results, a tree coverage of around 40% may be a feasible and optimized urban greenery scheme.
Abstract
A forest canopy model is developed and coupled into the Regional Boundary Layer Model (RBLM) to fully consider the vertical structure of tree morphology. Instead of a slab surface model formerly used to represent trees in RBLM, the new version allows refinement of the radiation budgets as well as sensible and latent heat fluxes and, hence, more precise simulation of the thermal impacts of tree plantings on urban meteorological behavior. By applying this new version of RBLM, sensitivity tests are conducted to explore the potential impacts of different greenery scenarios on the thermal environment in an eastern Chinese city, Suzhou, during hot summer days. Greenings, both tree planting and grass surfacing, are beneficial in cooling the ambient air temperature. In general, tree planting is more beneficial than grass surfacing with the same coverage. In terms of surface energy balance, with tree coverage increasing from 0% to 20%, and then to 40%, the average surface net radiation fluxes at noon (1200 LST) are 591, 512, and 421 W m−2, respectively. Correspondingly, the Bowen ratio is reduced from 8.78 to 1.20 and then to 0.43 as result of the redistribution of solar energy absorbed at the ground. The cooling effect of trees is more significant at noontime and can remarkably lower the daily maximum air temperature in urban areas. The cooling effect of urban greenery increases with its coverage. Using the study results, a tree coverage of around 40% may be a feasible and optimized urban greenery scheme.
