Impact of upstream urbanization on the urban heat island effects along the Washington-Baltimore corridor

In this study, the impact of upstream urbanization on enhanced UHI effects is examined using surface observations and numerical simulations of an extreme UHI event that occurred on 9 July 2007 over Baltimore, Maryland. Under southwesterly wind, Baltimore experienced higher peak surface temperatures and higher pollution concentrations than did the larger urban area of Washington, DC.

Results from a coupled ultra-high resolution mesoscale - urban canopy model with 2001 National Land Cover Data (NLCD) show an advective contribution from upstream urbanization to the UHI event. This dynamical process is demonstrated by replacing Baltimore or its upstream urban areas by natural vegetation (in the model), indicating that the UHI effects could be reduced by as much as 25%. An analysis of the urban-Bay interaction reveals the importance of horizontal wind direction in determining the intensity of Bay breezes and the urban boundary layer structures.