Analysis and simulation of wintertime light scattering by the urban aerosol in Dallas-Fort Worth

Wintertime atmospheric light scattering in Dallas, TX, was estimated throug h the use of aerosol models. Input data for the aerosol models were provide d by measurements of aerosol chemistry, physical particle size distribution s, and distributions of particulate sulfur by particle size, and by predict ions by an atmospheric simulation model. Light scattering measurements prov ided a basis for testing the aerosol models. The SCAPE thermodynamic equili brium model was used to estimate the amount of liquid water associated with particles and the ELSIE Mie scattering model was applied to estimate the r esulting light scattering. The calculations were based on aerosol propertie s measured in Dallas during December 1994 and February 1995, and changes in scattering due to hypothetical changes in the aerosol were predicted. The predicted light scattering was compared to scattering measured by an Optec nephelometer; agreement was within 20% in every case.