CHIR1 (Chiricahua National Monument, AZ, Lat. 32.0089, Long. -109.3891, Alt. 1570)

6 years aerosol data are available in Chiricahua National Monument during the sampling period of 1997 - 2002. As shown in Figure 1, the overall average total light extinction coefficient (Bext) is 27.3 Mm-1 (Visual Range ~  143 Km; Deciview ~ 10.0). The average PM2.5 mass concentration is 4.2 mg/m3. The average light extinction coefficient is relatively low, with ~37% of the light extinction is due to rayleigh gas scattering. The average contributions of the major aerosol components to Chiricahua National Monument haze are particulate sulfate 25.1%, nitrate 3.4%, organic matter (OMC) 12.9%, elemental carbon (light absorbing carbon, LAC) 4.6%, fine soil 3.7% and coarse mass (CM) 13.6%. 

Bext = 27.3 Mm-1

 

Figure 1 Average contributions of major aerosol chemical components to light extinction (1997-2002)  

 

Figure 2 Average contributions of major aerosol chemical components to light extinction in 20% best, middle 60% and 20% worst days (1997-2002)

As Figure 2 indicates, the average aerosol light extinction coefficient (Bext – Rayleigh Scattering (10 Mm-1)) during the 20% worst days is 30.2 Mm-1, which is about 3.6 times of the value of 8.3 Mm-1 during the 20% best days and 1.9 times of the value of 15.9 Mm-1 during the middle 60% days. Sulfate is the largest contributor to aerosol light extinction during the 20% worst days, and the contribution of sulfate to aerosol light extinction is  ~ 38.3% in worst days. CM and OMC also contribute ~ 23.9% and ~ 21.4% to aerosol light extinction during the worst days.

Figure 3 suggests that the highest occurrence of the 20% worst days happened in August, in which ~50% of the sampling days are the 20% haziest days at Chiricahua National Monument. As shown in Figure 4, sulfate is the largest aerosol contributors to haze during the Summer. In February, March and April, CM is the largest aerosol contributor to haze. OMC contributes ~20 - 30% to haze in January, May and June. Both CM and Sulfate are important from October to December.

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Figure 3 Percentage of sampling days that are 20% worst days in each month (1997-2002)

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Figure 4 Average contributions of major aerosol chemical components to light extinction during 20% worst days in each month (1997-2002)