Airborne Detection of Iodine Oxide and Glyoxal in the Free Troposphere over the Remote Tropical Pacific Ocean

We present the first spectral proof for the presence of iodine oxide (IO) and glyoxal (CHOCHO) in the free troposphere. Measurements were conducted with the University of Colorado Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument aboard the NSF/NCAR GV research aircraft (HIAPER) over the remote tropical Pacific Ocean. As part of the HEFT-10 instrument test program a research flight was conducted on 29 January 2010 out of Hawaii to the equatorial Pacific Ocean south of Hawaii. IO and CHOCHO were observed in the marine boundary layer as well as in the free troposphere up to 14km altitude. Satellite data of the same area give inconsistent values and are inconclusive on the vertical distribution. Our measurements for the first time retrieve the vertical distribution of IO and CHOCHO over the remote tropical Pacific Ocean by means of experimentally well constrained inverse radiative transfer modeling.