As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm^-1)) during the 20% worst days is 54.9 Mm^-1, which is about 14.2 times of the value of 3.9 Mm^-1 during the 20% best days and 4.9 times of the value of 11.3 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  ~ 60% in worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~56% of the sampling days are the 20% haziest days at Crater Lake National Park. As shown in Figure 4, OMC is the largest aerosol contributor to haze in July and August, with a contribution of ~60%. LAC also contributes more than 10% to haze during this period. Moreover, the light extinction coefficients during the 20% worst days are much higher in July and August than other time period of the year. This suggests that specific pollution events such as forest fires may be the major reason for the haze in the summer time.