Authors

Argonne National Laboratory
Jeff Camp
Jack Shannon

Summary

The Visibility Effects Module calculates visual impairment as expressed in visual range or deciviews of haze for a set of seven selected receptors.  Seasonal and annual distributions of daily visual impairment are produced from input of estimated atmospheric concentrations of sulfate and nitrate from the Atmospheric Pathways Module.  Output of visual impairment statistics is provided to the Scenario Benefits Module.

The Visibility Module is based on the Visibility Assessment Scoping Model (VASM) initially developed by E. Trexler at DOE.  BASM uses Monte Carlo techniques to produce short-term variations of visual impairment based on seasonal lognormal distribution parameters of the six important particulate species (sulfate, nitrate, elemental carbon, organic carbon, fine-particle dust, and carse-particle dust), relative humidity distribution statistics from climatology, and modeled changes in the seasonal means of the sulfate and nitrate concentrations.  The short-term concentration variations are combined with species-specific attenuation relationships that are functions of concentration and relative humidity.  Either mean conditions of visual impairment or frequencies above or below clean or dirty thresholds of interest may be examined.

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