Abstract:

Formaldehyde (HCHO) directly affects the atmospheric oxidative capacity through its effects onHOx. In remote marine environments, such as the tropical western Pacific (TWP), it is particularly importantto understand the processes controlling the abundance of HCHO because model output from these regions isused to correct satellite retrievals of HCHO. Here we have used observations from the Convective Transport ofActive Species in the Tropics (CONTRAST)field campaign, conducted during January and February 2014, toevaluate our understanding of the processes controlling the distribution of HCHO in the TWP as well as itsrepresentation in chemical transport/climate models. Observed HCHO mixing ratios varied from ~500 partsper trillion by volume (pptv) near the surface to ~75 pptv in the upper troposphere. Recent convectivetransport of near surface HCHO and its precursors, acetaldehyde and possibly methyl hydroperoxide,increased upper tropospheric HCHO mixing ratios by ~33% (22 pptv); this air contained roughly 60% less NOthan more aged air.Output from the CAM-Chem chemistry transport model (2014 meteorology)as well asninechemistry climate models from the Chemistry-Climate Model Initiative (free-running meteorology) are foundto uniformly underestimate HCHO columns derived from in situ observations by between 4 and 50%. Thisunderestimate of HCHO likely results from a near factor of two underestimate of NO in most models, whichstrongly suggests errors in NOxemissions inventories and/or in the model chemical mechanisms. Likewise, thelack of oceanic acetaldehyde emissions and potential errors in the model acetaldehyde chemistry lead toadditional underestimates in modeled HCHO of up to 75 pptv (~15%) in the lower troposphere.

Author affiliation: Anderson, Daniel C.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos

Author affiliation: Nicely, Julie M.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos. University Space Research; Estados Unidos

Author affiliation: Wolfe, Glenn M.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos. National Aeronautics and Space Administration; Estados Unidos

Author affiliation: Hanisco, Thomas F.. National Aeronautics and Space Administration; Estados Unidos

Author affiliation: Salawitch, Ross J.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos

Author affiliation: Canty, Timothy P.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos

Author affiliation: Dickerson, Russell R.. University of Maryland. Department of Atmospheric and Oceanic Science; Estados Unidos

Author affiliation: Apel, Eric C.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados Unidos

Author affiliation: Baidar, Sunil. State University of Colorado at Boulder; Estados Unidos. Cooperative Institute for Research in Environmental Sciences; Estados Unidos

Author affiliation: Bannan, Thomas J.. University of Manchester; Reino Unido

Author affiliation: Blake, Nicola J.. University of California; Estados Unidos

Author affiliation: Chen, Dexian. Georgia Institute of Techology; Estados Unidos

Author affiliation: Dix, Barbara. State University of Colorado at Boulder; Estados Unidos

Author affiliation: Fernandez, Rafael Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Institute of Physical Chemistry Rocasolano,; España

Author affiliation: Hall, Samuel R.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados Unidos

Author affiliation: Hornbrook, Rebecca S.. National Center For Atmospheric Research. Amospheric Chemistry División; Estados Unidos

Author affiliation: Huey, L. Gregory. Georgia Institute of Techology; Estados Unidos

Author affiliation: Josse, Beatrice. Centre National de Recherche Météorologique; Francia

Author affiliation: Jöckel, Patrick. Deutsches Zentrum für Luft‐ und Raumfahrt, Institut für Physik der Atmosphäre; Alemania

Author affiliation: Kinnison, Douglas E.. National Center for Atmospheric Research; Estados Unidos

Author affiliation: Koenig, Theodore K.. State University of Colorado at Boulder; Estados Unidos

Author affiliation: Le Breton, Michael. University of Gothenburg; Suecia

Author affiliation: Marécal, Virginie. Centre National de Recherche Météorologique; Francia

Author affiliation: Morgenstern, Olaf. National Institute of Water and Atmospheric Research; Nueva Zelanda

Author affiliation: Oman, Luke D.. National Aeronautics and Space Administration; Estados Unidos

Author affiliation: Pan, Laura L.. National Center for Atmospheric Research; Estados Unidos

Author affiliation: Percival, Carl. University of Manchester; Reino Unido

Author affiliation: Plummer, David. Canadian Centre for Climate Modeling and Analysis; Canadá

Author affiliation: Revell, Laura E.. Institute for Atmospheric and Climate Science; Suiza

Author affiliation: Rozanov, Eugene. Physikalisch-meteorologisches Observatorium Davos World Radiation Center; Suiza

Author affiliation: Saiz-lopez, Alfonso. Consejo Superior de Investigaciones Científicas. Instituto de Química Física; España

Author affiliation: Stenke, Andrea. Eth Zürich; Suiza

Author affiliation: Sudo, Kengo. Japan Agency For Marin-earth Science And Technology; Japón

Author affiliation: Tilmes, Simone. National Center for Atmospheric Research; Estados Unidos

Author affiliation: Ullmann, Kirk. National Center for Atmospheric Research; Estados Unidos

Author affiliation: Volkamer, Rainer. State University of Colorado at Boulder; Estados Unidos

Author affiliation: Weinheimer, Andrew J.. National Center for Atmospheric Research; Estados Unidos

Author affiliation: Zeng, Guang. National Institute Of Water And Atmospheric Research; Nueva Zelanda