Background Air Quality Modeling Results

CAMx Base 2011 US Background Simulation

We ran a CAMx sensitivity simulation derived from the 3SAQS 2011 Base version A CAMx (CAMx_3SAQS_Base11a) configuration to estimate background air quality in the U.S. The CAMx 2011 U.S. Background simulation (CAMx_3SAQS_Base11a_USBG) is an emissions sensitivity in which all anthropogenic emissions sources in the U.S. are removed. The only emissions included in the USBG simulation include:

• Canadian and Mexican anthropogenic sources
• Domain-wide biogenic sources
• Domain-wide wildfires (prescribed and ag fires are excluded)
• Domain-wide windblown dust
• Seasalt
• Lightning NOx

Table 1 presents summary results comparing monthly averaged daily maximum 8-hour average O3 (MDA8) from simulations Base11a and Base11a_USGB. Bar plots compare MDA8 averaged for each month and annually across all of the AQS monitors in the 12-km domain and within each of the Western states. The delta plots in Figure 1 show the monthly and annual differences in MDA8 between the Base11a and Base11a_USBG simulations.

Table 1. AQS Base and Background Monthly Mean MDA8