Preprints
https://doi.org/10.5194/acp-2020-998
https://doi.org/10.5194/acp-2020-998

  20 Nov 2020

20 Nov 2020

Review status: this preprint is currently under review for the journal ACP.

Observations of iodine monoxide over three summers at the Indian Antarctic bases, Bharati and Maitri

Anoop S. Mahajan1, Mriganka S. Biswas1,2, Steffen Beirle3, Thomas Wagner3, Anja Schönhardt4, Nuria Benavent5, and Alfonso Saiz-Lopez5 Anoop S. Mahajan et al.
  • 1Centre for Climate Change Research, Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, 411008 India
  • 2Savitribai Phule Pune University, Pune, 411008 India
  • 3Max-Planck-Institut für Chemie (MPI-C), Satellitenfernerkundung, 55128 Mainz, Germany
  • 4Institute of Environmental Physics, Department of Physics and Electrical Engineering, University of Bremen, Bremen, 330440 Germany
  • 5Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain

Abstract. Iodine plays a vital role in oxidation chemistry over Antarctica, with past observations showing highly elevated levels of iodine oxide (IO) leading to severe depletion of boundary layer ozone in West Antarctica. Here, we present multi axis differential absorption spectroscopy (MAX-DOAS) based observations of IO over three summers (2015–2017) at the Indian Antarctic bases, Bharati and Maitri. IO was observed during all the campaigns, with mixing ratios below 2 pptv for the three summers, which are lower than the peak levels observed in West Antarctica. This suggests that sources in West Antarctica are different or stronger than sources of iodine compounds in East Antarctica. Vertical profiles estimated using a profile retrieval algorithm showed decreasing gradients, with a peak in the lower boundary layer. The ground-based instrument retrieved vertical column densities (VCDs) were approximately a factor of three-five higher than the VCDs reported using satellite-based instruments, which is most likely related to the sensitivities of the measurement techniques. Airmass back-trajectory analysis failed to highlight a source region, with most of the airmasses coming from coastal or continental regions. This study highlights the variation in iodine chemistry in different regions in Antarctica and the importance of a long-term dataset to validate models estimating the impacts of iodine chemistry.

Anoop S. Mahajan et al.

 
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Anoop S. Mahajan et al.

Anoop S. Mahajan et al.

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Short summary
Iodine plays a vital role in oxidation chemistry over Antarctica, with past observations showing highly elevated levels of iodine oxide (IO) leading to severe depletion of boundary layer ozone. We present IO observations over three summers (2015–2017) at the Indian Antarctic bases, Bharati and Maitri. IO was observed during all campaigns, with mixing ratios below 2 pptv, which are lower than the peak levels observed in West Antarctica showing the differences in regional chemistry and emissions.
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