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Spatial and temporal variability of iodine in aerosol
  • +6
  • Juan Carlos Gomez Martin,
  • Alfonso Saiz-Lopez,
  • Carlos Alberto Cuevas,
  • Rafael Pedro Fernandez,
  • Benjamin Silas Gilfedder,
  • Rolf Weller,
  • Alex R. Baker,
  • Elise Droste,
  • Senchao Lai
Juan Carlos Gomez Martin
Instituto de AstrofĂ­sica de AndalucĂ­a

Corresponding Author:[email protected]

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Alfonso Saiz-Lopez
Spanish National Research Council (CSIC)
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Carlos Alberto Cuevas
Spanish National Research Council (CSIC)
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Rafael Pedro Fernandez
National Research Council (CONICET)
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Benjamin Silas Gilfedder
Universtiy of Bayreuth
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Rolf Weller
Alfred-Wegener-Institute
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Alex R. Baker
University of East Anglia
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Elise Droste
University of East Anglia
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Senchao Lai
South China University of Technology
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Abstract

In this work we describe the compilation and homogenization of an extensive dataset of aerosol iodine field observations in the period between 1963 and 2018 and we discuss the spatial and temporal dependences of total iodine in bulk aerosol by comparing the observations with CAM-Chem model simulations. Total iodine in aerosol shows a distinct latitudinal dependence, with an enhancement towards the northern hemisphere (NH) tropics and lower values towards the poles. This behavior, which has been predicted by atmospheric models to depend on the global distribution of the main oceanic iodine source (which in turn depends on the reaction of surface ozone with aqueous iodide on the sea water-air interface, generating gas-phase I2 and HOI), is confirmed here by field observations for the first time. Longitudinally, there is some indication of a wave-one profile in the Tropics, which peaks in the Atlantic and shows a minimum in the Pacific, following the wave-one longitudinal variation of tropical tropospheric ozone. New data from Antarctica show that the south polar seasonal variation of iodine in aerosol mirrors that observed previously in the Arctic, with two equinoctial maxima and the dominant maximum occurring in spring. While no clear seasonal variability is observed in NH middle latitudes, there is an indication of different seasonal cycles in the NH tropical Atlantic and Pacific. A weak positive long-term trend is observed in the tropical annual averages, which is consistent with an enhancement of the anthropogenic ozone-driven global oceanic source of iodine over the last 50 years.