Atmospheric Chemicals and Their Reactions
The presence and reactions of atmospheric chemicals affect conditions at the ground level. MSI PI Dylan Millet (Professor, Soil, Water, and Climate) studies these chemicals. He uses MSI resources for a range of projects that aim to improve understanding of the chemical composition of the atmosphere, how it is affected by humans and by natural processes, and the implications for health, air pollution, and climate change.
In recent research, Professor Millet and researchers from the U of M, Jet Propulsion Laboratory, and the Harvard University and Smithsonian Institution Center for Astrophysics have modeled hydroxyl radical (OH) trends and patterns of variability over forest ecosystems. They used satellite-based measurements of isoprene and formaldehyde for the years 2012-2020 to find changes in OH, and were able to attribute them to emission trends, biotic stressors, and climate. The study gives insights into how changing emissions and climate will have effects on atmospheric oxidation. The paper can be found on the website of the journal Science Advances: Joshua D. Shutter, Dylan B. Millet, Kelley C. Wells, Vivienne H. Payne, Caroline R. Nowlan, Gonzalo González Abad. Interannual changes in atmospheric oxidation over forests determined from space. Science Advances 10(20) (2024). doi: 10.1126/sciadv.adn1115.
In another study published recently in Nature Communications, Professor Millet and colleagues from the NASA Jet Propulsion Laboratory, BAER Institute, the Royal Belgian Institute for Space Aeronomy, Atmospheric and Environmental Research, and the Chinese Academy of Sciences used machine learning to convert satellite-based radiance observations into measurements of ethane in the atmosphere. Ethane is the most abundant non-methane hydrocarbon in the troposphere. MSI Scientific Computing Consultant Dr. David Porter also worked on this project. A story about this research appears on the U of M News site: Mapping fossil fuel emissions from space. The paper can be found on the journal website: Jared F. Brewer, Dylan B. Millet, Kelley C. Wells, Vivienne H. Payne, Susan Kulawik, Corinne Vigouroux, Karen E. Cady-Pereira, Rick Pernak, Minqiang Zhou. Space-based observations of tropospheric ethane map emissions from fossil fuel extraction. Nature Communications 15: 7829 (2024). doi: 10.1038/s41467-024-52247-z.
Image description: Spatial distribution of isoprene:formaldehyde (ΩISOP:ΩHCHO) column ratios over the Southeast US for July 2013 and 2020 and the 2020–2013 difference. Results are plotted separately for the CrIS/OMPS observations (A to C) and for the GEOS-Chem model predictions (D to F). Also mapped are the corresponding OH fields simulated by GEOS-Chem in the planetary boundary layer (PBL) (G to I). Image and description: Shutter, JD, et al. Science Advances 10(20) (2024), doi: 10.1126/sciadv.adn1115.
