Land cover influences on below-canopy temperatures in and near Baltimore, MD

In addition to two National Weather Service ASOS stations, weather variables including temperature are being measured continuously at five sites near Baltimore, MD. The measurements include temperature at the 1.5-meter height at all stations. At the five non-ASOS sites, measurements have been continuous since June 2003. These sites include one in a large open pasture, a nearby woodlot, a residential area with heavy tree cover but few buildings, a lawn area with nearby trees near a large apartment complex, and a residential area with some trees and large lawn areas. The ASOS sites are in downtown Baltimore and at the Baltimore/Washington International Airport (BWI). Temperature differences on an hourly basis between each site and the downtown ASOS site are being related empirically by regression analysis to upwind tree, impervious, and water cover out to 5 km from the National Land Cover Data (NLCD) 2001 database. Additional predictor variables for temperature difference are atmospheric stability (Turner Class, derived from BWI cloud and wind speed data), vapor pressure deficit, antecedent precipitation, and sky view and transmitted direct beam solar radiation estimated from hemispherical photographs at each site. The initial analysis is for May through September 2004. During this period, the downtown site was generally warmer than the other sites, with the temperature difference between the downtown and more-rural sites being as large as 11 ^ºC. The anticipated application is a GIS model of temperature differences across the city based on NLCD 30-m by 30-m imagery. The GIS mapping will be applied to times of special interest, such as early evening, when temperature differences are greatest, and mid-afternoon, when temperatures are maximum.