Mapping hydroxyl variability throughout the global remote troposphere via synthesis of airborne and satellite formaldehyde observations

Mapping hydroxyl variability throughout the global remote troposphere via synthesis of airborne and satellite formaldehyde observations

The hydroxyl radical (OH) fuels tropospheric ozone production and governs the lifetime of methane and many other gases. Existing methods to quantify global OH are limited to annual and global-to-hemispheric averages. Finer resolution is essential for isolating model deficiencies and building process...

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Published in:Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 23; pp. 11171 - 11180
Main Authors: Wolfe, Glenn M., Nicely, Julie M., St. Clair, Jason M., Hanisco, Thomas F., Liao, Jin, Oman, Luke D., Brune, William B., Miller, David, Thames, Alexander, Abad, Gonzalo González, Ryerson, Thomas B., Thompson, Chelsea R., Peischl, Jeff, McCain, Kathryn, Sweeney, Colm, Wennberg, Paul O., Kim, Michelle, Crounse, John D., Hall, Samuel R., Ullmann, Kirk, Diskin, Glenn, Bui, Paul, Chang, Cecilia, Dean-Day, Jonathan
Format: Journal Article
Language:English
Published: United States National Academy of Sciences 04-06-2019
Series:PNAS Plus
Subjects:
Formaldehyde
Gases
Hemispheres
Hydroxyl radicals
Mapping
Methane
Oxidation
Physical Sciences
PNAS Plus
Satellite observation
Seasonal variations
Spatial distribution
Synthesis
Tropical depressions
Troposphere
Variability
hydroxyl
OMI
formaldehyde
troposphere
ATom
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Summary:The hydroxyl radical (OH) fuels tropospheric ozone production and governs the lifetime of methane and many other gases. Existing methods to quantify global OH are limited to annual and global-to-hemispheric averages. Finer resolution is essential for isolating model deficiencies and building process-level understanding. In situ observations from the Atmospheric Tomography (ATom) mission demonstrate that remote tropospheric OH is tightly coupled to the production and loss of formaldehyde (HCHO), a major hydrocarbon oxidation product. Synthesis of this relationship with satellite-based HCHO retrievals and model-derived HCHO loss frequencies yields a map of total-column OH abundance throughout the remote troposphere (up to 70% of tropospheric mass) over the first two ATom missions (August 2016 and February 2017). This dataset offers unique insights on near-global oxidizing capacity. OH exhibits significant seasonality within individual hemispheres, but the domain mean concentration is nearly identical for both seasons (1.03 ± 0.25 × 106 cm−3), and the biseasonal average North/South Hemisphere ratio is 0.89 ± 0.06, consistent with a balance of OH sources and sinks across the remote troposphere. Regional phenomena are also highlighted, such as a 10-fold OH depression in the Tropical West Pacific and enhancements in the East Pacific and South Atlantic. This method is complementary to budget-based global OH constraints and can help elucidate the spatial and temporal variability of OH production and methane loss.
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Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved April 22, 2019 (received for review December 19, 2018)
Author contributions: G.M.W. and J.M.N. designed research; G.M.W., J.M.N., T.F.H., L.D.O., W.B.B., D.M., A.T., G.G.A., T.B.R., C.R.T., J.P., K.M., C.S., P.O.W., M.K., J.D.C., S.R.H., K.U., G.D., P.B., and C.C. performed research; G.M.W., J.M.N., J.M.S.C., J.L., and J.D.-D. analyzed data; G.M.W. wrote the paper; G.M.W., J.M.S.C., T.F.H., W.B.B., D.M., A.T., T.B.R., C.R.T., J.P., K.M., C.S., P.O.W., M.K., J.D.C., S.R.H., K.U., G.D., P.B., C.C., and J.D.-D. contributed to ATom observations; L.D.O. provided GMI model output; and G.G.A. provided OMI retrievals.
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.1821661116