EGUsphere EGUsphere EGUsphere EGUsphere 1867-8610 Copernicus Publications Göttingen, Germany 10.5194/egusphere-2025-1190 A systematic comparison of ACE-FTS <em>&delta;</em>D retrievals with airborne in situ sampling Clouser Benjamin Wade https://orcid.org/0000-0002-0323-6620 1 KleinStern Carly Cyd 2 Desmoulin Adrien https://orcid.org/0009-0004-4788-9553 1 Singer Clare E. https://orcid.org/0000-0002-1708-0997 1 St. Clair Jason M. https://orcid.org/0000-0002-9367-5749 3 4 Hanisco Thomas F. https://orcid.org/0000-0001-9434-8507 3 Sayres David S. 5 Moyer Elisabeth J. 1 Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA Department of Physics, University of Chicago, Chicago, IL, USA Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA GESTAR-II, University of Maryland Baltimore County, Baltimore, MD, USA Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA 04 04 2025 2025 1 25 Copyright: © 2025 Benjamin Wade Clouser et al. 2025 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1190/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1190/egusphere-2025-1190.pdf

The isotopic composition of water vapor in the upper troposphere and lower stratosphere (UTLS) can be used to understand and constrain the budget and pathways of water transport into that region of the atmosphere. Measurements of the water isotopic composition help further understanding of the region's chemistry, radiative budget, and the sublimation and growth of polar stratospheric clouds and high-altitude cirrus, both of which are also important to stratospheric chemistry and Earth's radiation budget. Here we present the first intercomparison of water isotopic composition <em>&delta;</em>D using in situ measurements from the ChiWIS, Harvard ICOS, and Hoxotope instruments and satellite retrievals from ACE-FTS. The in situ data comes from the AVE-WIIF, TC4, CR-AVE, StratoClim, and ACCLIP field campaigns, and satellite retrievals of isotopic composition are derived from the ACE-FTS v5.2 data set. We find that in all campaign intervals, the satellite retrievals above about 14 km altitude are depleted by up to 150 &permil; with respect to in situ measurements. We also use in situ measurements from the ChiWIS instrument, which has flown in both the Asian Summer Monsoon (AM) and the North American Monsoon (NAM), to confirm the isotopic enhancement in <em>&delta;</em>D observed in satellite retrievals above the NAM.

 Directorate for Geosciences OISE-1743753