SAGA1 (San Gabriel, CA, Lat. 34.2909, Long. -118.0282, Alt. 1791) Print-Friendly Version Print-Friendly Version (B&W)
1 year and 1 month aerosol data are available in San Gabriel during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 45.5 Mm-1 (Visual Range ~ 86 Km; Deciview ~ 15.2). The average PM2.5 mass concentration is 5.1 mg/m3. The average contributions of the major aerosol components to San Gabriel haze are particulate sulfate 17.4%, nitrate 25.4%, organic matter (OMC) 14.6%, elemental carbon (light absorbing carbon, LAC) 5.3%, fine soil 1.7% and coarse mass (CM) 13.6%.
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 71.4 Mm-1, which is about 7.2 times of the value of 9.9 Mm-1 during the 20% best days and 2.2 times of the value of 31.8 Mm-1 during the middle 60% days. Nitrate is the largest contributor to aerosol light extinction, with a contribution of 37% in the 20% worst days. CM also contributes about 22% to the aerosol light extinction in the 20% 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 San Gabriel. As shown in Figure 4, OMC is the largest aerosol contributor to haze in August, with a contribution of ~ 50%. Nitrate is the largest aerosol contributor to haze except in June to September, and December. Its contribution is about 30-60% in the worst days. OMC is the largest contributor in September. Very high CM concentration is found in December. But fine soil concentration is relatively low at the same time. Further analysis is needed to explain this.
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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