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 68.0 Mm^-1, which is about 7.9 times of the value of 8.6 Mm^-1 during the 20% best days and 3.1 times of the value of 22.1 Mm^-1 during the middle 60% days. OMC is the largest contributor to aerosol light extinction, with a contribution of 43% in the 20% worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in January and October, in which ~43% of the sampling days are the 20% haziest days at Starkey. As shown in Figure 4, nitrate is the largest aerosol contributor to haze during the 20% worst days in the winter, with a contribution of 45% during the 20% worst days. Nitrate and OMC both contribute about 30% in the 20% worst days in November. OMC is the largest aerosol contributor to haze in the 20% worst days in the rest of the year.

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)