20 years of ClO measurements in the Antarctic lower stratosp

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Title20 years of ClO measurements in the Antarctic lower stratosphereAbstractWe present 20 years (1996-2015) of austral springtime measurements of chlorine monoxide (ClO) over Antarctica from the Chlorine Oxide Experiment (ChlOE1) ground-based millimeter wave spectrometer at Scott Base, Antarctica, as well 12 years (2004-2015) of ClO measurements from the Aura Microwave Limb Sounder (MLS). From August onwards we observe a strong increase in lower stratospheric ClO, with a peak column amount usually occurring in early September. From mid-September onwards we observe a strong decrease in ClO. In order to study interannual differences, we focus on a 3-week period from 28 August to 17 September for each year and compare the average column ClO anomalies. These column ClO anomalies are shown to be highly correlated with the average ozone mass deficit for September and October of each year. We also show that anomalies in column ClO are strongly anti-correlated with 30hPa temperature anomalies, both on a daily and an interannual timescale. Making use of this anti-correlation we calculate the linear dependence of the interannual variations in column ClO on interannual variations in temperature. By making use of this relationship, we can better estimate the underlying trend in the total chlorine (Cly = HCl+ClONO2 + HOCl+2 x Cl2+2 x Cl2O2 + ClO+Cl). The resultant trends in Cly, which determine the long-term trend in ClO, are estimated to be -0.5 ± 0.2, -1.4 ± 0.9, and -0.6 ± 0.4%year-1, for zonal MLS, Scott Base MLS (both 2004-2015), and ChlOE (1996-2015) respectively. These trends are within 1σ of trends in stratospheric Cly previously found at other latitudes. The decrease in ClO is consistent with the trend expected from regulations enacted under the Montreal Protocol. Copyright Author(s) 2016.AcknowledgementsThis project was funded by NASA under the Upper Atmosphere Research Program, by the Naval Research Laboratory, and by the Office of Naval Research. We would like to acknowledge the many Antarctica New Zealand technicians who have supported the daily operation of ChlOE over two decades of measurements. We also acknowledge the logistical support that Antarctica New Zealand has supplied over this period. Work at the Jet Propulsion Laboratory, California Institute of Technology, was carried out under a contract with the National Aeronautics and Space Administration. Sonde temperature data were collected under support from the National Science Foundation. The data used in this publication were obtained as part of the Network for the Detection of Atmospheric Composition Change (NDACC) and are publicly available (see http://www.ndacc.org).Funding DetailsAntarctica New Zealand; ONR, Office of Naval Research

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1st AuthorNedoluha, G.AuthorNedoluha, G.Connor, B.Mooney, T.Barrett, J.Parrish, A.Gomez, R.Boyd, I.Allen, D.Kotkamp, M.Kremser, S.Deshler, T.Newman, P.Santee, M.Year2016JournalAtmospheric Chemistry and PhysicsVolume16Number16Pages10725-10734DOI10.5194/acp-16-10725-2016URLhttps://www.scopus.com/inward/recor.....9a4bb466804a7fb4f3a7683dfKeywordsrank5ProgrammeK085 - Remote sensing and sampling of atmospheric trace gases and greenhouse gases

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TypeArticleCitationNedoluha, G., Connor, B., Mooney, T., Barrett, J., Parrish, A., Gomez, R., Boyd, I., Allen, D., Kotkamp, M., Kremser, S., Deshler, T., Newman, P. and Santee, M. (2016). 20 years of ClO measurements in the Antarctic lower stratosphere. Atmospheric Chemistry and Physics, 16(16): 10725-10734 IdentifierNedoluha2016Relevancerank5