SULA1 (Sula (Selway Bitteroot Wilderness), MT, Lat. 45.8598, Long. -114, Alt. 1903) Print-Friendly Version Print-Friendly Version (B&W)
2 year and 6 month aerosol data are available in Sula (Selway Bitteroot Wilderness) during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 23.3 Mm-1 (Visual Range ~ 167 Km; Deciview ~ 8.5). The average PM2.5 mass concentration is 2.9 mg/m3. The average contributions of the major aerosol components to Sula (Selway Bitteroot Wilderness) haze are particulate sulfate 16.0%, nitrate 5.3%, organic matter (OMC) 22.9%, elemental carbon (light absorbing carbon, LAC) 5.6%, fine soil 2.1% and coarse mass (CM) 5.1%.
Figure 1 Average contributions of major aerosol chemical components to light extinction (Based on data available in 1997-2002) (B&W)
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) (Data Table) (B&W)
As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm-1)) during the 20% worst days is 28.7 Mm-1, which is about 7.6 times of the value of 3.8 Mm-1 during the 20% best days and 2.6 times of the value of 11.1 Mm-1 during the middle 60% days. OMC is the largest contributor to aerosol light extinction, with a contribution of 48% in the 20% worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~73% of the sampling days are the 20% haziest days at Sula (Selway Bitteroot Wilderness). As shown in Figure 4, OMC is the largest aerosol contributor to haze during the 20% worst days in month of May to October, with a contribution of 23 - 57% during the 20% worst days. Sulfate is the largest aerosol contributor to haze in the 20% worst days in the rest of the year except December. Nitrate is the largest aerosol contributor to haze in December, though the occurrence of the worst days is relatively low.
Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 1997-2002) (Data Table) (B&W)
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) (Data Table) (B&W)
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