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 38.6 Mm^-1, which is about 11.5 times of the value of 3.4 Mm^-1 during the 20% best days and 3.2 times of the value of 11.9 Mm^-1 during the middle 60% days. OMC is the largest contributor to aerosol light extinction during the 20% worst days, and the contribution of OMC to aerosol light extinction is  ~ 45.8% in worst days. Sulfate also contributes about 20% in the worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in April, August and November, in which ~ 40% of the sampling days are the 20% haziest days at Pasayten Wilderness Area. As shown in Figure 4, sulfate is the largest aerosol contributor to haze in April, with a contribution of ~ 30% in the 20% worst days. OMC contributes ~ 47% and 34% to haze in the 20% worst days in August and November, and is the largest contributor to haze. Nitrate also contributes 21% to haze in the 20% worst days in November. 

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)