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Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution
E V Fischer1, D J Jacob2, R M Yantosca2
1Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA.
Atmospheric Chemistry and Physics
|March 24, 2021
Summary
Peroxyacetyl nitrate (PAN) is a key atmospheric reservoir for nitrogen oxide radicals (NOx). Improved modeling of non-methane volatile organic compounds (NMVOCs) in GEOS-Chem successfully simulates PAN observations, advancing our understanding of atmospheric chemistry.
Area of Science:
- Atmospheric chemistry and transport
- Global atmospheric modeling
- Ozone and oxidant distributions
Background:
- Peroxyacetyl nitrate (PAN) is the primary tropospheric reservoir for nitrogen oxide radicals (NOx).
- PAN facilitates NOx transport, impacting global ozone and hydroxyl radical (OH) distributions.
- Simulating PAN in global models is challenging due to complex NMVOC sources and chemistry.
Purpose of the Study:
- To improve the simulation of PAN in a global chemical transport model.
- To identify key precursors and emission sources of PAN.
- To validate model performance against global aircraft observations.
Main Methods:
- Utilized an improved representation of non-methane volatile organic compounds (NMVOCs) in the GEOS-Chem model.
- Compared model simulations with PAN observations from worldwide aircraft campaigns.
- Analyzed the contributions of various carbonyl precursors and NMVOC emission sources to PAN formation.
Main Results:
- The improved GEOS-Chem model successfully simulates observed PAN concentrations globally.
- Acetaldehyde, methylglyoxal, and acetone are major carbonyl precursors for PAN.
- Isoprene and alkanes are significant NMVOC emission sources for PAN, with anthropogenic sources dominating in the extratropics.
- Lightning NOx drives the PAN maximum in the South Atlantic free troposphere.
Conclusions:
- Advanced NMVOC chemistry representation is crucial for accurate PAN simulation in global models.
- PAN plays a vital role in the remote tropospheric NOx budget.
- Understanding PAN formation pathways is essential for predicting global ozone and oxidant levels.
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