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 28.2 Mm^-1, which is about 3.7 times of the value of 7.7 Mm^-1 during the 20% best days and 1.9 times of the value of 14.6 Mm^-1 during the middle 60% days. Sulfate, OMC and CM are three of the largest contributors to aerosol light extinction during the 20% worst days, and the contribution of sulfate, OMC and CM to aerosol light extinction are  ~ 28.8%, 25.0% and 24.0%, respectively in the 20% worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in April to June and August to September, in which ~30 - 40% of the sampling days are the 20% haziest days at Great Sand Dunes National Monument. As shown in Figure 4, Dust (CM + fine soil) is the largest aerosol contributor to haze in the spring, with a contribution of ~ 30 - 40% in the worst days. OMC, CM  and sulfate are all important aerosol contributors to haze in June and August, each with a contribution of 20% in the worst days. Sulfate contributes ~ 35% to haze in the worst days in September, and is the largest aerosol contributor.

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)