Increasing co-occurrence of fine particulate matter and ground-level ozone extremes in the western United States

Dmitri A Kalashnikov; Jordan L Schnell; John T Abatzoglou; Daniel L Swain; Deepti Singh

doi:10.1126/sciadv.abi9386

Increasing co-occurrence of fine particulate matter and ground-level ozone extremes in the western United States

Sci Adv. 2022 Jan 7;8(1):eabi9386. doi: 10.1126/sciadv.abi9386. Epub 2022 Jan 5.

Authors

Dmitri A Kalashnikov¹, Jordan L Schnell², John T Abatzoglou³, Daniel L Swain^{4

5

6}, Deepti Singh¹

Affiliations

¹ School of the Environment, Washington State University Vancouver, Vancouver, WA, USA.
² Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, NOAA/Global Systems Laboratory, Boulder, CO, USA.
³ Management of Complex Systems Department, University of California, Merced, Merced, CA, USA.
⁴ Institute of the Environment and Sustainability, University of California, Los Angeles, Los Angeles, CA, USA.
⁵ Capacity Center for Climate and Weather Extremes, National Center for Atmospheric Research, Boulder, CO, USA.
⁶ The Nature Conservancy of California, San Francisco, CA, USA.

Abstract

Wildfires and meteorological conditions influence the co-occurrence of multiple harmful air pollutants including fine particulate matter (PM_2.5) and ground-level ozone. We examine the spatiotemporal characteristics of PM_2.5/ozone co-occurrences and associated population exposure in the western United States (US). The frequency, spatial extent, and temporal persistence of extreme PM_2.5/ozone co-occurrences have increased significantly between 2001 and 2020, increasing annual population exposure to multiple harmful air pollutants by ~25 million person-days/year. Using a clustering methodology to characterize daily weather patterns, we identify significant increases in atmospheric ridging patterns conducive to widespread PM_2.5/ozone co-occurrences and population exposure. We further link the spatial extent of co-occurrence to the extent of extreme heat and wildfires. Our results suggest an increasing potential for co-occurring air pollution episodes in the western US with continued climate change.