Eighth Symposium on the Urban Environment
Timothy R. Oke Symposium


The EPiCC Vancouver Experiment—how do urban vegetation characteristics and garden irrigation control the local-scale energy balance?

Andreas Christen, University of British Columbia, Vancouver, BC, Canada; and B. Crawford, N. R. Goodwin, R. Tooke, N. Coops, S. Grimmond, T. R. Oke, and J. A. Voogt

The Environmental Prediction in Canadian Cities (EPiCC) network is seeking to improve Canada's weather forecasting system for urban areas and to establish models that will support a better system for conserving of resources in cities (Voogt et al., same conference). Whilst the performance of current urban canopy parameterizations has been excellent at several relatively dry sites in densely-built areas - it has been less tested and less successful at more vegetated sites with extensive irrigation. The role of anthropogenic water release associated with irrigation / sprinkling of urban green-space can be large in suburban residential areas, rivaling precipitation as the main source of external water availability (Oke et al., same conference). The wet-dry contrasts of adjacent urban surfaces that result from irrigation and paving are further known to boost evaporation in a non-linear fashion.

Data from two contrasting neighborhoods in Vancouver, BC, Canada were used in combination with data from a rural reference site to explore the effect of urban vegetation and garden irrigation on the surface energy balance partitioning in cities. Both suburban neighborhoods are composed of single-family residences, but one neighborhood has substantially less vegetation, less irrigation, and approximately twice the number of homes per area. Each of the two neighborhoods features simultaneously operated towers that provide data on net all-wave radiation, sensible and latent heat fluxes (by means of eddy covariance). At eight residential lawns - that are typical for the footprint of the two towers - soil hydrology sites have been installed. The soil hydrology sites feature each a TDR system, soil temperature, soil-heat flux, and surface wetness sensors as well as water meters (water consumption of a single home) for a range of irrigation regimes and management practices. Additionally, a rural site with similar instrumentation over non-managed and non-irrigated grassland serves as a reference case. Detailed spatial information in a 1 km circle around the flux towers is available from airborne LIDAR measurements and satellite imagery.

In this presentation, we discuss first results from a one-month intensive observation period in summer 2008. We relate the observed integral energy balance partitioning at tower tops to surface characteristics and patchiness, to the surface water balance, and to rural reference conditions.

extended abstract  Extended Abstract (868K)

wrf recording  Recorded presentation

Joint Session 9, Urban Energy Balance
Monday, 12 January 2009, 1:30 PM-2:30 PM, Room 124A

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