Extended Abstract (400K)7.1
Sensitivity of surface-atmosphere energy exchanges in urban areas derived from simulations
Sarah M. Roberts, University of British Columbia, Vancouver, BC, Canada; and T. R. Oke, A. Lemonsu, C. S. B. Grimmond, and P. Jackson
Understanding the nature of energy partitioning at the surface of cities is prerequisite to gaining proper insight and ability to model their climatic environment and impacts. Observational studies, while allowing for general awareness of urban surface-atmosphere interactions, are often limited in their applicability to other sites and/or processes. To overcome this, numerical models which aim to simulate urban climatology have been developed. The Town Energy Balance (TEB) model of Masson (2000) seeks to couple the micro- and meso-scales and to accurately represent the urban energy budget in meso-scale atmospheric models. TEB uses local canyon geometry together with surface and substrate radiative, thermal, moisture and roughness properties to simulate the effects produced by the presence of buildings and it is forced with atmospheric and radiation data from above-roof level. The whole urban system is simulated by calculating individual energy balances for walls, roads, and roofs, which are then integrated to resolve the local-scale surface energy balance. The model has been independently evaluated using measured flux values from three dry urban sites – the downtown city center of Mexico City, a light industrial site in Vancouver, Canada (Masson et al., 2002) and the city center of Marseille, France (Lemonsu et al., 2003). At these sites, the model simulated net radiation to within less than 10 W m-2 and its partitioning into turbulent and storage fluxes to within a few tens of W m-2.
TEB’s good performance points towards its promise to conduct further analyses, including sensitivity tests, to better understand the primary criteria affecting local-scale urban surface-atmosphere energy exchanges (flow regime, surface geometry and structure). Such an analysis is performed for a dense, dry site in Marseille and the results reveal that the wind regime plays a significant role in surface-atmosphere energy partitioning in this environment, whereas varying urban geometry, surface thermal parameters, and surface radiative properties do not greatly impact the relative degree of surface-atmosphere sensible heat sharing.
Session 7, Modeling Urban Land Surfaces and Buildings: Part 2 (Room 611)
Wednesday, 14 January 2004, 8:30 AM-9:30 AM, Room 611
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