MELA1 (Medicine Lake, MT, Lat. 48.4872, Long. -104.4756, Alt. 605) Print-Friendly Version Print-Friendly Version (B&W)
3 years aerosol data are available in Medicine Lake during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 36.7 Mm-1 (Visual Range ~ 106 Km; Deciview ~ 13.0). The average PM2.5 mass concentration is 4.2 mg/m3. The average contributions of the major aerosol components to Medicine Lake haze are particulate sulfate 27.7%, nitrate 18.2%, organic matter (OMC) 11.6%, elemental carbon (light absorbing carbon, LAC) 3.8%, fine soil 1.7% and coarse mass (CM) 9.8%.
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 49.8 Mm-1, which is about 4.5 times of the value of 11.1 Mm-1 during the 20% best days and 2.1 times of the value of 23.9 Mm-1 during the middle 60% days. Sulfate and nitrate are two of the largest contributors to aerosol light extinction during the 20% worst days, and the contributions of sulfate and nitrate to aerosol light extinction are ~ 37.2% and 32.5% in worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in January, in which ~ 40% of the sampling days are the 20% haziest days at Medicine Lake. As shown in Figure 4, during the winter, early spring and later fall, both nitrate and sulfate contribute ~ 30 - 45% to regional haze in the 20% worst days. While in the summer, later spring and early fall, sulfate, OMC, and CM are important contributors to haze.
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)
