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 28.5 Mm^-1, which is about 8.2 times of the value of 3.5 Mm^-1 during the 20% best days and 2.9 times of the value of 9.8 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  ~ 49.4% in worst days. Sulfate also contributes 22.4% to aerosol light extinction.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~60% of the sampling days are the 20% haziest days at Gates of the Mountains. As shown in Figure 4, OMC is the largest aerosol contributor to haze in the summer, with a contribution of ~ 50% in the worst days in July and August.

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)