Observations of iodine monoxide columns from satellite

Abstract

Abstract. Iodine species in the troposphere are linked to ozone depletion and new particle formation. In this study, a full year of iodine monoxide (IO) columns retrieved from measurements of the SCIAMACHY satellite instrument is presented, coupled with a discussion of their uncertainties and the detection limits. The largest amounts of IO are found near springtime in the Antarctic. A seasonal variation of iodine monoxide in Antarctica is revealed with high values in springtime, slightly less IO in the summer period and again larger amounts in autumn. In winter, no elevated IO levels are found in the areas accessible to satellite measurements. This seasonal cycle is in good agreement with recent groundbased measurements in Antarctica. In the Arctic region, no elevated IO levels were found in the period analysed. This implies that different conditions with respect to iodine release exist in the two Polar Regions. To investigate possible release mechanisms, comparisons of IO columns with those of tropospheric BrO, and ice coverage are described and discussed. Some parallels and interesting differences between IO and BrO temporal and spatial distributions are identified. Overall, the large spatial coverage of satellite retrieved IO data and the availability of a long-term dataset provide new insight about the abundances and distributions of iodine compounds in the troposphere.

Detection of iodine monoxide in the tropical free troposphere

“…The conversion of measured satellite SCDs into VCDs is often based on the assumption that trace gases are only located in the MBL (2,11,13,17). Based on our profiles, the satellite VCDs could be lower by a factor of 1.5-3, depending on cloud fraction (expressed as VCD bias in Table 1).…”

“…Emissions of reactive iodine species over the remote ocean remain poorly understood (11,14) but are currently thought to be associated with primary production from biological sources (2,(14)(15)(16). Satellite maps of IO over tropical oceans (17) support the notion that iodine sources are mostly related to biological activity (2). However, the quantitative use of satellite IO data to infer iodine sources over oceans is currently limited by missing information about vertical distributions, because the satellite sensitivity varies over the height of the air column.…”

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

“…Frieß et al, 2001;Peters et al, 2005;Zingler and Platt, 2005;SaizLopez et al, 2006SaizLopez et al, , 2007bRead et al, 2008). Only recently, space-borne observations confirmed enhanced levels of IO near coastal Antarctica (Saiz-Lopez et al, 2007a;Schönhardt et al, 2008). Removal of iodine-bearing compounds from the gas-phase can occur through uptake by aerosols and through nucleation of new particles initiated by polymerization of iodine oxides (e.g.…”

Observations of high concentrations of I2 and IO in coastal air supporting iodine‐oxide driven coastal new particle formation

“…Significant levels of molecular iodine have been observed at Mace Head and nearby sites ($100 parts per trillion (ppt)) [Saiz-Lopez and Plane, 2004;Saiz-Lopez et al, 2006;Peters et al, 2005], and at La Jolla, California ($8 ppt) [Finley and Saltzman, 2008]. Although large-scale I 2 observations have not been realized so far due to the lack of analytical techniques to accurately measure this species, the measurements of iodine monoxide (IO) radicals, an unambiguous product of iodine atom reaction with ozone, have been carried out at various coastal sites and the polar regions by ground-based approaches and satellite [e.g., Peters et al, 2005;Whalley et al, 2007;Schönhardt et al, 2008].…”