edu.ucar.opensky::articles:24317 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-25T06:28:27.139993 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d75142mf https://doi.org/10.25326/DAS4-7Q54 https Related Dataset #1 Atmospheric simulation chamber study: formaldehyde+methanediol + OH - Gas-phase oxidation - product study - 2018-06-28 Ubiquitous atmospheric production of organic acids mediated by cloud droplets 2021-05-13T00:00:00Z publication https://n2t.org/ark:/85065/d75142mf https://doi.org/10.1038/s41586-021-03462-x Franco, B. author Blumenstock, T. author Cho, C. author Clarisse, L. author Clerbaux, C. author Coheur, P. author De Mazière, M. author De Smedt, I. author Dorn, H. author Emmerichs, T. author Fuchs, H. author Gkatzelis, G. author Griffith, D. W. T. author Gromov, S. author Hannigan, James W. author Hase, F. author Hohaus, T. author Jones, N. author Kerkweg, A. author Kiendler-Scharr, A. author Lutsch, E. author Mahieu, E. author Novelli, A. author Ortega, Ivan author Paton-Walsh, C. author Pommier, M. author Pozzer, A. author Reimer, D. author Rosanka, S. author Sander, R. author Schneider, M. author Strong, K. author Tillmann, R. author Van Roozendael, M. author Vereecken, L. author Vigouroux, C. author Wahner, A. author Taraborrelli, D. author UCAR/NCAR - Library publisher Atmospheric acidity is increasingly determined by carbon dioxide and organic acids1,2,3. Among the latter, formic acid facilitates the nucleation of cloud droplets4 and contributes to the acidity of clouds and rainwater1,5. At present, chemistry–climate models greatly underestimate the atmospheric burden of formic acid, because key processes related to its sources and sinks remain poorly understood2,6,7,8,9. Here we present atmospheric chamber experiments that show that formaldehyde is efficiently converted to gaseous formic acid via a multiphase pathway that involves its hydrated form, methanediol. In warm cloud droplets, methanediol undergoes fast outgassing but slow dehydration. Using a chemistry–climate model, we estimate that the gas-phase oxidation of methanediol produces up to four times more formic acid than all other known chemical sources combined. Our findings reconcile model predictions and measurements of formic acid abundance. The additional formic acid burden increases atmospheric acidity by reducing the pH of clouds and rainwater by up to 0.3. The diol mechanism presented here probably applies to other aldehydes and may help to explain the high atmospheric levels of other organic acids that affect aerosol growth and cloud evolution. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. None eng geoscientificInformation