A Vegetated Urban Canopy Model for Meteorological and Environmental Modelling |
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| Authors: | Sang-Hyun Lee Soon-Ung Park |
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| Institution: | (1) School of Earth and Environmental Sciences, Seoul National University, San 56-1 Shilim-Dong Gwanak-Gu, Seoul, South Korea |
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| Abstract: | An urban canopy model is developed for use in mesoscale meteorological and environmental modelling. The urban geometry is
composed of simple homogeneous buildings characterized by the canyon aspect ratio (h/w) as well as the canyon vegetation characterized by the leaf aspect ratio (σ
l
) and leaf area density profile. Five energy exchanging surfaces (roof, wall, road, leaf, soil) are considered in the model,
and energy conservation relations are applied to each component. In addition, the temperature and specific humidity of canopy
air are predicted without the assumption of thermal equilibrium. For radiative transfer within the canyon, multiple reflections
for shortwave radiation and one reflection for longwave radiation are considered, while the shadowing and absorption of radiation
due to the canyon vegetation are computed by using the transmissivity and the leaf area density profile function. The model
is evaluated using field measurements in Vancouver, British Columbia and Marseille, France. Results show that the model quite
well simulates the observations of surface temperatures, canopy air temperature and specific humidity, momentum flux, net
radiation, and energy partitioning into turbulent fluxes and storage heat flux. Sensitivity tests show that the canyon vegetation
has a large influence not only on surface temperatures but also on the partitioning of sensible and latent heat fluxes. In
addition, the surface energy balance can be affected by soil moisture content and leaf area index as well as the fraction
of vegetation. These results suggest that a proper parameterization of the canyon vegetation is prerequisite for urban modelling. |
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| Keywords: | Canyon vegetation Leaf area index Mesoscale environmental modelling Multiple reflection Surface energy balance Urban canopy model |
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