• pollution;
  • shadowing;
  • numerical modeling;
  • solar radiation

Abstract Areas of high concentrations of particulates in the urban atmosphere are hypothesized to strongly influence the solar receipt in nearby nonpolluted regions. Reductions of solar radiation in nonpolluted areas by upsun high aerosol regions are computed using a three-dimensional multi-scattering radiation model for specified solar-elevation classes. Numerical simulations from this model indicate that reductions exceeding 10 percent can occur several kilometers downsun of even moderately polluted regions in the early morning (i.e., periods of low solar-elevation angle). Although the reductions in global radiation are quite pronounced in the early day, they are generally overwhelmed in the daily total because of the relatively small amount of radiation associated with low-elevation angles. A series of simulations for three representative latitudes (33°N, 43°N and 53°N) demonstrate that the areal extent of the shadowing is highly dependent on latitude. Reductions in solar radiation exceeding 3 percent occur 15 km down range of the center of pollution for high-latitude (53°N) locations during early-morning, low-elevation angle periods. Such excessive solar attenuation in nonpolluted regions may affect the site selection of solar power facilities, the planning and siting of parks, golf courses and other recreational activities, the migration and tourism trends in areas experiencing seasonal population changes (i.e., the sunbelt states), and the temperature regime of the region.