Roles of Urban Tree Canopy and Buildings in Urban Heat Island Effects: Parameterization and Preliminary Results

• DOI: 10.1175/jamc-d-11-0228.1
• Publication Date: 2012-05-07T12:59:26Z
• Authors: Christopher P. Lo...; Dale J. Allen; Da-Lin Zhang; Kenneth E. Pickering; Russell R. Dickerson; Laura Landry
• Keywords: Urban Heat Island; Shading; Tree canopy; Microclimate; Street Canyon

Abstract Urban heat island (UHI) effects can strengthen waves and air pollution episodes. In this study, the dampening impact of urban trees on UHI during an extreme wave in Washington, D.C., Baltimore, Maryland, metropolitan area is examined by incorporating trees, soil, grass into coupled Weather Research Forecasting model canopy (WRF-UCM). By parameterizing these natural surfaces alongside roadways buildings, modified WRF-UCM used to investigate how dampen UHI. The was run with 50% tree cover over roads a 10% decrease width streets make space for soil buildings. Results show that, averaged all areas, added vegetation decreases surface temperature street canyons 4.1 K road-surface building-wall temperatures 15.4 8.9 K, respectively, as result shading evapotranspiration. These changes propagate downwind alter gradient associated Chesapeake Bay breeze and, therefore, strength bay breeze. building height shows that decreasing commercial heights 8 m residential 2.5 results up 0.4-K higher daytime near-surface because less 1.2-K lower nighttime longwave radiative trapping canyons.