Atmos. Chem. Phys. Discuss., 11, 27833-27860, 2011
© Author(s) 2011. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Iodine monoxide in the north subtropical free troposphere
O. Puentedura1, M. Gil1, A. Saiz-Lopez2, T. Hay2, M. Navarro-Comas1, A. Gómez-Pelaez3, E. Cuevas3, and J. Iglesias1
1Instituto Nacional de Técnica Aeroespacial (INTA), Area de Investigación e Instrumentación Atmosférica, Ctra Ajalvir km4, 28850, Torrejón de Ardoz, Madrid, Spain
2Laboratory for Atmospheric and Climate Science, CSIC, Toledo, Spain
3Centro de Investigación Atmosférica de Izaña (Agencia Estatal de Meteorología – AEMET), Sta. Cruz de Tenerife, Spain

Abstract. Iodine monoxide (IO) was retrieved using a new multi-axis DOAS instrument deployed at the Izaña subtropical observatory as part of the Network for the Detection of Atmospheric Composition Change (NDACC) programme. The station is located at 2370 m a.s.l., well above the trade wind inversion that limits the top of the marine boundary layer, and is hence representative of the free troposphere. We report daily observations from May to August 2010 at different viewing angles. During this period, the spectral signature of IO was unequivocally detected on every day of measurement. A mean IO differential slant column density (DSCD) of 1.2 × 1013 molecules cm−2 was observed at 5° instrument elevation angle (IEA) on clear days using a single zenith reference for the reported period, with a day-to-day variability of 12% at 1 standard deviation. At an IEA of 0°, the mean DSCD value for clear days is 2.0 × 1013 molecules cm−2, with a day-to-day variability of 14%. Based on simultaneous O4 measurements, the IO mixing ratio is estimated to be 0.18 pptv in the free troposphere at an IEA of 5°. Episodes of Saharan dust outbreaks were also observed, with large increases in the DSCDs at higher elevation angles, suggesting an enhancement of IO inside the dust cloud.

Citation: Puentedura, O., Gil, M., Saiz-Lopez, A., Hay, T., Navarro-Comas, M., Gómez-Pelaez, A., Cuevas, E., and Iglesias, J.: Iodine monoxide in the north subtropical free troposphere, Atmos. Chem. Phys. Discuss., 11, 27833-27860, doi:10.5194/acpd-11-27833-2011, 2011.
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