IO in the Lower Stratosphere and Vertical Profiles over the Tropical Eastern and Western Pacific
Theodore Konstantinos Koenig1, Rainer M Volkamer2, Sunil Baidar3, Barbara Dix4, Mathew J Evans5, Lucy Carpenter6, Tomás Sherwen5, Douglas Edward Kinnison7, J F Lamarque8, Alfonso Saiz-Lopez9, Eric C Apel10, Rebecca S Hornbrook7, Elliot L Atlas11, Laura Pan12, Ross J Salawitch13 and The CONTRAST and TORERO Teams, (1)University of Colorado at Boulder, Department of Chemistry and Biochemistry, Boulder, CO, United States, (2)University of Colorado Boulder, Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Chemistry, Boulder, United States, (3)CIRES, University of Colorado Boulder/NOAA Chemical Sciences Laboratory, Boulder, CO, United States, (4)University of Colorado at Boulder, CIRES, Boulder, United States, (5)University of York, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, York, United Kingdom, (6)Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, United Kingdom, (7)NCAR, Boulder, CO, United States, (8)National Center for Atmospheric Research, Boulder, CO, United States, (9)Spanish National Research Council, Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Blas Cabrera (CSIC), Madrid, Spain, (10)National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling Laboratory, Boulder, United States, (11)University of Miami, Miami, United States, (12)National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling, Boulder, United States, (13)University of Maryland College Park, Department of Chemistry and Biochemistry, College Park, MD, United States
Abstract:
Iodine Monoxide (IO) is a halogen radical species that catalytically destroys ozone, modifies the atmosphere’s oxidative capacity and is a precursor to aerosol particle formation and growth. Measurements of IO are generally scarce, and only very few observations have recently detected IO as widespread in the tropical free troposphere. Here we report on IO observations by the CU Airborne MAX-DOAS instrument aboard the NSF/NCAR GV aircraft during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOC (TORERO) field campaigns. We have measured IO vertical profiles over the tropical and sub-tropical Western and Eastern Pacific Ocean, including a detection of IO in the UTLS and lower stratosphere. Our measurements indicate IO abundances that are 2-3 times higher in the Southern hemisphere than in the Northern hemisphere free troposphere. Measurements in the lower stratosphere and tropical UTLS provide the first quantification of IO in these layers by limb observations of scattered sunlight. We compare these observations with predictions from the global models CAMChem and GEOSChem.
