SYCA1 (Sycamore Canyon, AZ, Lat. 35.1406, Long. -111.9693, Alt. 2040)
2 year and 9 month aerosol data are available in Sycamore Canyon during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 33.9 Mm-1 (Visual Range ~ 115 Km; Deciview ~ 12.2). The average PM2.5 mass concentration is 7.0 mg/m3. The average contributions of the major aerosol components to Sycamore Canyon haze are particulate sulfate 14.2%, nitrate 5.1%, organic matter (OMC) 19.6%, elemental carbon (light absorbing carbon, LAC) 7.6%, fine soil 10.3% and coarse mass (CM) 13.8%.
Figure 1 Average contributions of major aerosol chemical components to light extinction (Based on data available in 1997-2002)
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)
As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm-1)) during the 20% worst days is 45.4 Mm-1, which is about 4.5 times of the value of 10.1 Mm-1 during the 20% best days and 2.1 times of the value of 21.3 Mm-1 during the middle 60% days. OMC and CM are two of the largest contributors to aerosol light extinction, with a contribution of 31% and 26% in the 20% worst days.
Figure 3 suggests that the highest occurrence of the 20% worst days happened in June, in which ~54% of the sampling days are the 20% haziest days at Sycamore Canyon. As shown in Figure 4, CM and fine soil are the largest aerosol contributors to haze during the 20% worst days in June, with a contribution of 30% and 22% during the 20% worst days. Both dust (CM and fine soil) and OMC are important haze contributors in May, July and September, while OMC dominates in August, and October to December.
Figure 3 Percentage of sampling days that are 20% worst days in each month (Based on data available in 1997-2002)
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)