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 47.1 Mm^-1, which is about 9.2 times of the value of 5.2 Mm^-1 during the 20% best days and 3.2 times of the value of 14.7 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  ~ 54.9% in worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~ 52% of the sampling days are the 20% haziest days at Lava Beds. As shown in Figure 4, OMC is the largest aerosol contributor to haze in August, with a contribution of 59%. Relatively high aerosol loadings are found in July and August. OMC contributes about 63% to haze in the 20% worst days  in July, and LAC also contributes about 14%. This suggests that specific pollution events such as forest fires may be responsible for the haziest 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)