GH003-10
Increasing co-occurrence of particulate matter and surface ozone extremes during the wildfire season in the western United States

Wednesday, 9 December 2020: 07:27
Virtual
Dmitri Alexander Kalashnikov, Washington State University Vancouver, School of the Environment, Vancouver, WA, United States, Deepti Singh, Washington State University, School of the Environment, Vancouver, WA, United States, Jordan Schnell, Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, John T Abatzoglou, University of California Merced, Management of Complex Systems, Merced, CA, United States and Daniel L Swain, University of California Los Angeles, Los Angeles, CA, United States
Abstract:
Air pollution is an urgent global health problem resulting in millions of premature deaths annually. Co-occurrence of elevated levels of fine particulate matter (PM2.5) and surface ozone (O3) can lead to disproportionately higher human health impacts relative to their individual occurrences. Wildfires are a source of PM2.5 and O3 precursors, and increasing wildfire activity has already increased extreme PM2.5 levels in the western U.S. (WUS). However, trends in PM2.5/O3 co-occurrence, associated physical mechanisms and current population exposure to such conditions have not been investigated. In this work, we quantify the spatial and temporal characteristics of extreme PM2.5/O3 co-occurrence across the WUS during the wildfire season (April-September) and identify their large-scale drivers using observed PM2.5 and O3 (1° x 1°; 1999-2018) and ERA5 reanalysis datasets (0.25° x 0.25°; 1979-2019). We perform Self-Organizing Map (SOM) clustering of large-scale meteorological patterns (1979-2019) during the wildfire season and for each cluster, we quantify co-occurrences across the region along with the fraction of the population exposed to high PM2.5/O3 levels. We find that the large-scale weather patterns that amplify the risk of extreme PM2.5/O3 co-occurrence over areas affecting >10M people in the WUS show robust increasing trends in both frequency (+18.7 days) and persistence (+4.6 days) over the 41-y period. The most widespread co-occurrence events were associated with the 2017 and 2018 intense wildfire seasons, abnormally high frequency of favorable large-scale weather patterns and record warm conditions across much of the WUS. Our results show that there is increasing co-occurrence of PM2.5/O3 during the wildfire season highlighting the potential for compounding human health stressors with projected increases in warming, ridging, and wildfire activity in the WUS.
<< Previous Abstract | Next Abstract >>