IO in the Lower Stratosphere and Vertical Profiles over the Tropical Eastern and Western Pacific

Thursday, 18 December 2014: 3:10 PM
Theodore Konstantinos Koenig1, Rainer M Volkamer2, Sunil Baidar3, Barbara K Dix1, Mathew J Evans4, Lucy Carpenter4, Tomas Sherwen4, Douglas Edward Kinnison5, J F Lamarque6, Alfonso Saiz-Lopez7, Eric C Apel6, Rebecca S Hornbrook5, Elliot L Atlas8, Laura Pan6 and Ross J Salawitch9, (1)University of Colorado at Boulder, Department of Chemistry and Biochemistry, Boulder, CO, United States, (2)Univ. of Colorado, Boulder, Boulder, CO, United States, (3)University of Colorado at Boulder, Cooperate Institute for Research in Environmental Sciences, Boulder, CO, United States, (4)University of York, York, United Kingdom, (5)NCAR, Boulder, CO, United States, (6)National Center for Atmospheric Research, Boulder, CO, United States, (7)Spanish National Research Council, Zaragoza, Spain, (8)University Miami, Miami, FL, United States, (9)University of Maryland, College Park, MD, United States
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.