ROMO1 (Rocky Mountain National Park, CO, Lat. 40.2783, Long. -105.5456, Alt. 2755) 

6 years aerosol data are available in Rocky Mountain National Park during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 25.8 Mm-1 (Visual Range ~ 151 Km; Deciview ~ 9.5). The average PM2.5 mass concentration is 3.3 mg/m3. The average contributions of the major aerosol components to Rocky Mountain National Park haze are particulate sulfate 20.2%, nitrate 8.0%, organic matter (OMC) 16.0%, elemental carbon (light absorbing carbon, LAC) 5.5%, fine soil 2.6% and coarse mass (CM) 8.9%. 

Bext = 25.8 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 31.6 Mm-1, which is about 6.8 times of the value of 4.6 Mm-1 during the 20% best days and 2.3 times of the value of 14.0 Mm-1 during the middle 60% days.  Sulfate is the largest contributor to aerosol light extinction, with a contribution of 30% in the 20% worst days. OMC also contributes 28% to the aerosol light extinction in the 20% worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in July, in which ~ 46% of the sampling days are the 20% haziest days at Rocky Mountain National Park, and OMC and sulfate are two of the largest aerosol contributors to haze in the 20% worst days with a contributions of 30% and 19%, respectively. As shown in Figure 4, sulfate and nitrate are two of the largest aerosol contributor to haze in the 20% worst days in November to December and January to April, each with a contribution of 20 - 30%. For the rest of the year, OMC and sulfate are the largest aerosol contributors, both with a contribution of 20 - 30%.

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)