As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm^-1)) during the 20% worst days is 36.0 Mm^-1, which is about 3.7 times of the value of 9.8 Mm^-1 during the 20% best days and 2.0 times of the value of 18.2 Mm^-1 during the middle 60% days. Sulfate, organic matter and coarse mass 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  ~ 27.4% 24.1% and 17.8%, respectively in worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in January, June and August, in which ~30% of the sampling days are the 20% haziest days at Bosque del Apache. As shown in Figure 4, in the winter, nitrate dominates the aerosol light extinction, and contributes about 25% - 40% to haze during the 20% worst days. OMC is the largest aerosol contributor with a contribution of 25 - 30% in February, June and July. In the summer and fall from August to November, sulfate dominates the light extinction with a contribution of 30-35%.  In the spring time, the contributions of the coarse mass and fine soil are also important. Although April has the lowest occurrence of 20% worst days, the light extinction coefficients for the worst days in April are relatively high and dominated by dust (coarse and fine soil). This may due to the sparsely occurring dust storms in the spring, which significantly elevate the aerosol concentrations and result in regional haze in Bosque del Apache.