MOHO1 (Mount Hood, OR, Lat. 45.2927, Long. -121.7694, Alt. 1341) Print-Friendly Version Print-Friendly Version (B&W)
2 year and 9 month aerosol data are available in Mount Hood during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 25.3 Mm-1 (Visual Range ~ 154 Km; Deciview ~ 9.3). The average PM2.5 mass concentration is 2.4 mg/m3. The average contributions of the major aerosol components to Mount Hood haze are particulate sulfate 26.5%, nitrate 9.9%, organic matter (OMC) 14.5%, elemental carbon (light absorbing carbon, LAC) 4.7%, fine soil 1.2% and coarse mass (CM) 3.7%.
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 32.7 Mm-1, which is about 10.4 times of the value of 3.2 Mm-1 during the 20% best days and 2.5 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 ~ 39.6% in worst days. OMC also contributes 27.1% in the worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~ 50% of the sampling days are the 20% haziest days at Mount Hood. As shown in Figure 4, sulfate contributes ~ 20 - 40% to haze in the 20% worst days throughout the year. OMC contributes about 20 - 30% to haze in the summer during the 20% worst days, while nitrate contributes about 20 - 30% in the winter.
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)
