Smoke, Heatwaves and Ozone: A Historic Air Pollution Episode in the San Francisco Bay Area Captured by a Prototype of the Re-designed EPA Photochemical Assessment Monitoring System

The EPA recently revised the design of the Photochemical Assessment Monitoring System (PAMS) that will go in to effect in Summer. The new set of monitoring requirements and convergence with the NCore Multipollutant Monitoring Network means that many state and local air quality agencies will be routinely measuring aldehydes, speciated VOC, true-NO₂, NO, NO_y, trace-level CO, SO₂, PM mass and speciation, meteorology and mixed layer height all at a single site. The recent updates to PAMS also require states to develop an Enhanced Monitoring Plan (EMP), designed to add flexibility to the system and encourage collaboration with outside investigators. Here, we make use of a set of measurements made at various sites across the Bay Area in Fall 2017 to better understand the conditions that resulted in a 22-year record of maximum daily 8-hour average ozone concentration at the Hayward, CA, monitoring station. The measurements included in the analysis, continuous formaldehyde (Santa Clara, CA), the formaldehyde and NO₂ columns, ceilometer backscatter (Richmond, CA), and space-based measurements of aerosol optical depth (VIIRS) and NO₂ (OMI), help guide expectations for the redesigned PAMS network.