DENA1 (Denali National Park, AK, Lat. 63.7233, Long. -148.9675, Alt. 658.2 m)    

6 years aerosol data are available in Denali National Park during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 18.9 Mm-1 (Visual Range ~ 206 Km; Deciview ~ 6.4). The average PM2.5 mass concentration is 1.8 mg/m3. The overall aerosol light extinction is relative low in Denali National Park, and 52.8% of the light extinction is due to Rayleigh gas scattering. The average contributions of the major aerosol components to Denali National Park haze are particulate sulfate 16.7%, nitrate 2.3%, organic matter (OMC) 16.3%, elemental carbon (light absorbing carbon, LAC) 4.6%, fine soil 0.9% and coarse mass (CM) 6.4%. 

Bext = 18.9 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 20.8 Mm-1, which is about 7.6 times of the value of 2.7 Mm-1 during the 20% best days and 3.0 times of the value of 6.9 Mm-1 during the middle 60% days. OMC is the largest contributor to aerosol light extinction, with a contribution of 46% in the 20% worst days. Sulfate also contributes about 29% in the 20% worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in July, in which ~40% of the sampling days are the 20% haziest days at Denali National Park.  As shown in Figure 4, in July, OMC is the largest aerosol contributor to haze, with a contribution of ~ 47% during the 20% worst days. OMC is the largest aerosol contributor to haze in the 20% worst days from May to October, with a contribution of 22-47%. Sulfate is the largest one for the rest of the year, with a contribution of 20-35% in the worst days.

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)