Fourth Symposium on the Urban Environment


Impacts of urban land cover change on the Convective Boundary Layer (CBL) in Baltimore-Washington DC

Jimmy O. Adegoke, CIRA/Colorado State Univ., Fort Collins, CO; and K. Gallo, R. Pielke, L. Steyaert, and W. P. Kustas

The land-use and land cover (LULC) history of the Baltimore-Washington DC region has been intensively studied through a variety of environmental research collaborations and regional partnerships. Land cover data scenarios for 1900 and 1992/93 were developed to contrast the major land cover changes involving agriculture, forests, and especially the growth of the Baltimore and Washington, D.C. metropolitan areas over the past century. The land cover scenarios were used in modeling experiments with the Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS). The simulations were designed to diagnose the extent and spatial variability of anomalies in surface heat, moisture, and momentum and their effects on local and regional climate.

The experimental procedure adopted for this study took advantage of the grid-nesting capability of RAMS. A fine grid with 1km horizontal grid spacing was nested into a coarser 5 km grid, which extends from southern Pennsylvania, Maryland, to parts of Virginia, and West Virginia. Two sets of month-long simulations for July 2000 were conducted. First, we used satellite-derived land cover data from the United States Geological Survey (USGS) 1992/93 30 meters land cover data set for the conterminous United States as the lower boundary condition in a 31-day RAMS run. We then replaced this data with the pre-1900 land cover data for the same region and ran a similar RAMS simulation. Identical observed meteorology was retained for the lateral boundary conditions in both cases. The model results for the initial run were validated with July 2000 surface climate data and flux measurements of sensible and latent heat from sites located within the fine grid model domain.

Surface energy budget parameters, and spatially explicit fields of the available convective potential energy (CAPE) averaged over the integration period, are analyzed in the context of the driving human–induced land cover transformations of the last 100 years. The implications of these results for surface climate and land-use management practices in the greater Baltimore-Washington DC area are discussed.

Session 6, Mitigation of urban heat islands: scientific and regulatory aspects, implementation and cost-effectiveness issues, local perspectives, and quantification of environmental impacts.
Tuesday, 21 May 2002, 11:00 AM-2:14 PM

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