Iodine monoxide at a clean marine coastal site: observations of high frequency variations and inhomogeneous distributions R. Commane1,*, K. Seitz2, C. S. E. Bale1, W. J. Bloss3, J. Buxmann2, T. Ingham1,4, U. Platt2, D. Pöhler2, and D. E. Heard1,4 1School of Chemistry, University of Leeds, LS2 9JT, UK 2Institute of Environmental Physics, University of Heidelberg, Germany 3School of Geography, Earth and Environmental Sciences, University of Birmingham, B15 2TT, UK 4National Centre for Atmospheric Science, University of Leeds, Leeds, LS2 9JT, UK *now at: School of Engineering and Applied Sciences, Harvard University, MA, USA
Abstract. The first in situ point observations of iodine monoxide (IO) at a clean
marine site were made using a laser-induced fluorescence instrument
deployed at Mace Head, Ireland in August 2007. IO mixing ratios of up
to 49.8 pptv (equivalent to pmol mol−1; 1 s average)
were observed at day-time low tide, well in
excess of previous observed spatially-averaged maxima. A strong
anti-correlation of IO mixing ratios with tide height was evident and the high time
resolution of the observations showed IO peaked in the hour after low
tide. The temporal delay in peak IO compared to low tide has not been
observed previously but coincides with the time of peak aerosol number
previously observed at Mace Head.
A long path-differential optical absorption spectroscopy instrument
(with a 2 × 6.8 km folded path across Roundstone Bay) was
also based at the site for 3 days during the point measurement
observation period. Both instruments show similar temporal trends but
the point measurements of IO are a factor of ~6–10 times
greater than the spatially averaged IO mixing ratios, providing direct
empirical evidence of the presence of inhomogeneities in the IO mixing
ratio near the intertidal region.
Citation: Commane, R., Seitz, K., Bale, C. S. E., Bloss, W. J., Buxmann, J., Ingham, T., Platt, U., Pöhler, D., and Heard, D. E.: Iodine monoxide at a clean marine coastal site: observations of high frequency variations and inhomogeneous distributions, Atmos. Chem. Phys., 11, 6721-6733, doi:10.5194/acp-11-6721-2011, 2011.