Modeling Air Quality in the San Joaquin Valley during the 2013 DISCOVER-AQ Field Campaign

The San Joaquin Valley (SJV) in California frequently experiences elevated PM_2.5 concentrations during winter months. The DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign conducted by NASA took place in the SJV from January 16 to February 06, 2013. This campaign captured two elevated PM_2.5 events in Bakersfield where the 24-hour surface PM_2.5 exceeded 70 µg/m³ (more than double the 24-hour PM_2.5  Standard of 35 µg/m³). The campaign provided unparalleled surface, vertical and column measurements of a suite of gaseous and particulate pollutants in the SJV, which have not been available for over a decade since the last major PM field campaign (CRPAQS in 2000-2001). The U.S. EPA CMAQ model was used to investigate PM formation and buildup throughout the DISCOVER-AQ time period. Model performance will be presented for both surface and vertical profiles of a variety of gases (e.g., O₃, NOx, PAN, HNO₃, NH₃, HCHO and other selected VOCs) and PM species (e.g., nitrate, sulfate, ammonium, black carbon, and organic compounds (OC)), as well as the sensitivity of PM formation and buildup to the simulated meteorological fields. Areas for future model improvements will be also highlighted.