Abstract

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 res... Show moreWe 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 10km altitude. Satellite data of the same area give inconsistent values and are inconclusive on the vertical distribution. Our measurements retrieve for the first time the vertical distribution of IO and CHOCHO over the remote tropical Pacific Ocean by means of experimentally well constrained inverse radiative transfer modeling. Due to the very high solubility of the glyoxal molecule, concentrations in excess of 100ppt like we found over the open Pacific Ocean during a ship campaign, require an airborne source mechanism (Sinreich et al., 2010). The vertical distributions of CHOCHO, IO and HCHO and aerosol extinction provide independent means to investigate further the source mechanism for reactive gases in the tropical remote boundary layer, and in the free troposphere. We discuss their vertical distributions in relation to the aerosol profile, as well as consider local dynamics and air mass trajectories provided by the Weather Research and Forecast Model (WRF). Show less