Multiscale plume transport from collapse of the World Trade Center on September...
The collapse of the world trade center (WTC) produced enhanced levels
of airborne contaminants in New York City and nearby areas on September 11,
2001 through December, 2001. This catastrophic event revealed the vulnerability of
the urban environment, and the inability of many existing air monitoring systems to
operate efficiently in a crisis. The contaminants released circulated within the street
canyons, but were also lifted above the urban canopy and transported over large distances,
reflecting the fact that pollutant transport affects multiple scales, from single
buildings through city blocks to mesoscales. In this study, ground-and space-based
observations were combined with numerical weather forecast fields to initialize finescale
numerical simulations. The effort is aimed at reconstructing pollutant dispersion
from the WTC in New York City to surrounding areas, to provide means for eventually
evaluating its effect on population and environment. Atmospheric dynamics were
calculated with the multi-grid RegionalAtmosphericModeling System (RAMS), covering
scales from 250m to 300km and contaminant transport was studied using the
Hybrid Particle and Concentration Transport (HYPACT) model that accepts RAMS
meteorological output.TheRAMS/HYPACTresults were tested against PM2.5 observations
from the roofs of public schools in New York City (NYC), Landsat images,
and Multi-angle Imaging SpectroRadiometer (MISR) retrievals. Calculations accurately reproduced locations and timing of PM2.5 peak aerosol concentrations, as well
as plume directionality. By comparing calculated and observed concentrations, the
effective magnitude of the aerosol source was estimated. The simulated pollutant
distributions are being used to characterize levels of human exposure and associated
environmental health impacts.