CABI1 (Cabinet Mountains, MT, Lat. 47.955, Long. -115.6709, Alt. 1434) Print-Friendly Version Print-Friendly Version (B&W)
2 and a half years aerosol data are available in Cabinet Mountains during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 28.7 Mm-1 (Visual Range ~ 136 Km; Deciview ~ 10.5). The average PM2.5 mass concentration is 3.6 mg/m3. The average contributions of the major aerosol components to Cabinet Mountains haze are particulate sulfate 19.1%, nitrate 6.2%, organic matter (OMC) 25.8%, elemental carbon (light absorbing carbon, LAC) 6.2%, fine soil 2.1% and coarse mass (CM) 5.7%.
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 39.5 Mm-1, which is about 7.1 times of the value of 5.6 Mm-1 during the 20% best days and 2.5 times of the value of 15.8 Mm-1 during the middle 60% days. OMC and Sulfate are two of the largest contributors to aerosol light extinction during the 20% worst days, and the contribution of OMC and sulfate to aerosol light extinction are ~ 48.3% and 21.4% in worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in May, July, September and October, in which more than ~30% of the sampling days are the 20% haziest days at Cabinet Mountains. As shown in Figure 4, OMC is the largest aerosol contributor to haze from June to December, during which the contribution of OMC to haze is 30 - 60% in the worst days. Sulfate dominates the aerosol light extinction in March, April and May, and contributes ~ 25 - 35% to haze in the worst days. There is a big Bext peak in August with very high OC/EC concentrations, which may due to specific pollution events such as forest fires.
Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available 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 1997-2002) (Data Table) (B&W)
