Premium
The Global Budget of Atmospheric Methanol: New Constraints on Secondary, Oceanic, and Terrestrial Sources
Author(s) -
Bates Kelvin H.,
Jacob Daniel J.,
Wang Siyuan,
Hornbrook Rebecca S.,
Apel Eric C.,
Kim Michelle J.,
Millet Dylan B.,
Wells Kelley C.,
Chen Xin,
Brewer Jared F.,
Ray Eric A.,
Commane Róisín,
Diskin Glenn S.,
Wofsy Steven C.
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033439
Subject(s) - methanol , troposphere , formaldehyde , atmosphere (unit) , atmospheric chemistry , plume , tropospheric ozone , methane , ozone , atmospheric sciences , environmental science , chemistry , astrobiology , meteorology , geology , physics , organic chemistry
Abstract Methanol is the second‐most abundant organic gas in the remote atmosphere after methane, but its sources are poorly understood. Here, we report a global budget of methanol constrained by observations from the ATom aircraft campaign as implemented in the GEOS‐Chem global atmospheric chemistry model. ATom observations under background marine conditions can be fit in the model with a surface ocean methanol concentration of 61 nM and a methanol yield of 13% from the newly implemented CH 3 O 2 + OH reaction. While terrestrial biogenic emissions dominate the global atmospheric methanol budget, secondary production from CH 3 O 2 + OH and CH 3 O 2 + CH 3 O 2 accounts for 29% of the total methanol source, and makes up the majority of methanol in the background marine atmosphere sampled by ATom. Net emission from the ocean is comparatively minor, particularly because of rapid deposition from the marine boundary layer. Aged anthropogenic and pyrogenic plumes sampled in ATom featured large methanol enhancements to constrain the corresponding sources. Methanol enhancements in pyrogenic plumes did not decay with age, implying in‐plume secondary production. The atmospheric lifetime of methanol is only 5.3 days, reflecting losses of comparable magnitude from photooxidation and deposition. GEOS‐Chem model results indicate that methanol photochemistry contributes 5%, 4%, and 1.5% of the tropospheric burdens of formaldehyde, CO, and ozone, respectively, with particularly pronounced effects in the tropical upper troposphere. The CH 3 O 2 + OH reaction has substantial impacts on radical budgets throughout the troposphere and should be included in global atmospheric chemistry models.