Figure 2 Average contributions of major aerosol chemical components to light extinction in 20% best, middle 60% and 20% worst days (Based on data available in 1997-2002)

As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm^-1)) during the 20% worst days is 23.0 Mm^-1, which is about 4.2 times of the value of 5.5 Mm^-1 during the 20% best days and 1.9 times of the value of 11.8 Mm^-1 during the middle 60% days. Sulfate and OMC are two of the largest contributors to aerosol light extinction during the 20% worst days, and the contributions of sulfate and OMC to aerosol light extinction are  ~ 31.6% and 31.1% in worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in the summer and May, in which ~ 35% of the sampling days are the 20% haziest days at Mount Zirkel Wilderness. As shown in Figure 4, OMC is the largest aerosol contributor to haze in the summer, with a contribution of ~ 30% in the 20% worst days. Sulfate is the largest aerosol contributor to haze for the rest of the year except December, with a contribution of 25 - 40% in the 20% worst days. Both sulfate and CM contribute ~ 18% to haze in December.

Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 1997-2002)

Figure 4 Average contributions of major aerosol chemical components to light extinction during 20% worst days in each month (Based on data available in 1997-2002)