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Haze Metrics
Aerosol Eqs
Recon Bext
Humidity Corr.
Group 10,50,90
Haze Baseline
Collection Stat
Win Haze
Visual Plume

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Group 10, 50, 90 Visibility Indices

Procedures for calculating Group 10, 50, 90 values from aerosol and haze data.

IMPROVE aerosol data is the basis for calculating the visibility index used to track haze level trends under the regional haze rule. The index calculation involves summing the individual contributions to light extinction from each of five major fine particle species (sulfate, soil, organic carbon, elemental carbon, and nitrate) and from coarse mass. The index represents the average haziness (in deciviews) for the days with the highest 20% of aerosol calculated light extinction and for the days with the lowest 20% of aerosol calculated light extinction.

EPA has finalized the guidance documents for calculating the regional haze indices.  The guidance document "Tracking Progress Under the Regional Haze Rule: Guidance Document" contain a detailed description of the calculation procedures.