Impacts of large-scale surface modifications on meteorological conditions and energy use: A 10-region modeling study

This paper summarizes results from a mesoscale modeling study to quantify the possible meteorological and energy-use impacts of large-scale increases in surface albedo and vegetative fraction. Ten regions in the U.S. were characterized and simulated in base- and modified-surface conditions. Time- and space-dependent meteorological variables were simulated for each region in four 3-day episodes to represent a range of seasonal variations. In terms of peak summer conditions, for example, the mesoscale simulations suggest that at 2 pm local time, urban areas in Los Angeles, New York, Chicago, Atlanta, Washington DC, and Philadelphia can be up to 2 degrees C warmer than their rural surrounds, whereas Dallas and Houston can be 1.5 degrees C and Phoenix up to 1 degrees C warmer than rural areas. Miami does not exhibit a significant heat island. The simulations also suggest that large-scale increases in albedo and vegetative fraction can result in spatially-averaged decreases in 2-pm air temperature of 0.5 to 1.5 degrees C during a typical summer day, depending on region. Using a simple interpolative procedure, a complete year of hourly weather data was created for each region (based on episodic meteorological simulation results) and input into energy-use models. The modified weather input was used to assess the effects of large-scale albedo and vegetative fraction changes on annual energy consumption in each of the ten areas targeted in this study. The simulations suggest annual electricity savings of between 1 and 6.7 kWhm(-2) (of roof area) in residential neighbor hoods and between 2 and 6.1 kWhm(-2) in office areas, depending on region. Annual gas penalties amount to up to 34.8 MJ m(-2) (of roof area) in residential neighborhoods and up to 21.1 MJ m(-2) in office areas.