SEQU1 (Sequoia National Park, CA, Lat. 36.4894, Long. -118.8292, Alt. 535)         

6 years aerosol data are available in Sequoia National Park during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 60.3 Mm-1 (Visual Range ~ 65 Km; Deciview ~ 18.0). The average PM2.5 mass concentration is 9.2 mg/m3. The average contributions of the major aerosol components to Sequoia National Park haze are particulate sulfate 18.4%, nitrate 25.4%, organic matter (OMC) 22.3%, elemental carbon (light absorbing carbon, LAC) 7.4%, fine soil 1.7% and coarse mass (CM) 8.2%. 

Bext = 60.3 Mm-1

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 98.6 Mm-1, which is about 6.8 times of the value of 14.5 Mm-1 during the 20% best days and 2.2 times of the value of 45.6 Mm-1 during the middle 60% days. Nitrate is the largest contributor to aerosol light extinction, with a contribution of 46% in the 20% worst days. 

Figure 3 suggests that the highest occurrence of the 20% worst days happened in October, in which ~ 40% of the sampling days are the 20% haziest days at Sequoia National Park. As shown in Figure 4, Nitrate, OMC and sulfate each contributes ~ 20 - 25% to haze in the 20% worst days in October. Nitrate is the largest aerosol contributor to haze in the cold season. The contributions of sulfate and OMC increase as the weather warms up. Sulfate is the largest aerosol contributor in May and July, while OMC is the largest one in June, August and September.

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)