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 28.5 Mm^-1, which is about 3.4 times of the value of 8.4 Mm^-1 during the 20% best days and 1.7 times of the value of 16.9 Mm^-1 during the middle 60% days. Sulfate is the largest contributor to aerosol light extinction, with a contribution of 28% in the 20% worst days. CM and OMC also contribute 23% and 22%.

Figure 3 suggests that the occurrence of the 20% worst days is pretty constant from April to December, in which ~ 20 - 30% of the sampling days are the 20% haziest days at Ike's Backbone. As shown in Figure 4, CM is the largest aerosol contributor to haze in the 20% worst days from April to June, with a contribution of ~ 25%. Sulfate is the largest aerosol contributor from July to December, with a contribution of ~ 20 - 25% in the worst days. Nitrate is the largest aerosol contributor in January and February, with a contribution of ~ 27% in the worst days. OMC contributes about 15 - 20% to haze in the worst days from April to November.

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)