Evolution of Peroxyacetyl Nitrate (PAN) in wildfire smoke plumes
detected by the Cross-Track Infrared Sounder (CrIS) over the western
U.S. during summer 2018.
Abstract
We use new peroxyacetyl nitrate (PAN) observations from the Cross-Track
Infrared Sounder (CrIS) on the Suomi National Polar-orbiting Partnership
satellite to investigate PAN over the western U.S. during the summer
2018 North American wildfire season. This period coincides with the
Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and
Nitrogen (WE-CAN). When combined with favorable background conditions,
the resolution and sensitivity of CrIS is sufficient to observe PAN
production in plumes. CrIS PAN normalized excess mixing ratios (NEMRs)
in the Pole Creek Fire increase from 0.2% to 0.4% within 3-4 hours of
physical aging, consistent with NEMRs calculated from WE-CAN
observations. CrIS is also able to detect PAN and CO enhancements in
plumes that have been transported hours to days downwind. On average for
the study period, 24-56% of PAN in the free troposphere during the
afternoon over the western U.S. can be attributed to fires.