NOCA1 (North Cascades, WA, Lat. 48.7315, Long. -121.0645, Alt. 576) Print-Friendly Version Print-Friendly Version (B&W)
2 year and 10 month aerosol data are available in North Cascades during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 25.7 Mm-1 (Visual Range ~ 152 Km; Deciview ~ 9.4). The average PM2.5 mass concentration is 2.5 mg/m3. The average contributions of the major aerosol components to North Cascades haze are particulate sulfate 17.6%, nitrate 5.4%, organic matter (OMC) 14.0%, elemental carbon (light absorbing carbon, LAC) 4.4%, fine soil 0.8% and coarse mass (CM) 2.9%.
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 34.3 Mm-1, which is about 9.0 times of the value of 3.8 Mm-1 during the 20% best days and 2.6 times of the value of 13.3 Mm-1 during the middle 60% days. Sulfate is the largest contributor to aerosol light extinction during the 20% worst days, and the contribution of sulfate to aerosol light extinction is ~ 53% in worst days. OMC also contributes about 25% in the worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~ 60% of the sampling days are the 20% haziest days at North Cascades. As shown in Figure 4, sulfate is the largest aerosol contributor to haze in the summer, with a contribution of ~ 40% in the 20% worst days. One worst day happened in November 2000 with relatively high aerosol, especially OMC loading, which may be correspondent to a specific pollution event.
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)
