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| Titel |
Global 3-D model studies of tropospheric iodine |
| VerfasserIn |
Hannah Mantle, Martyn Chipperfield, Ryan Hossaini, Wuhu Feng, John Plane, Tom Breider, Graham Mann |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094842
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| Publikation (Nr.) |
 EGU/EGU2014-10275.pdf |
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| Zusammenfassung |
| Halogen species play an important role in tropospheric chemistry. Iodine is believed to enhance catalytic ozone loss (acting synergistically with bromine) and can lead to the formation of new particles. Recent observations have increased our knowledge on the role of iodine but key processes need to be tested and quantified by inclusion in numerical models.
We describe the development of an iodine chemistry scheme within the TOMCAT global 3-D chemical transport model (CTM). The existing model contained a detailed tropospheric chemistry scheme (including bromine) along with the GLOMAP aerosol scheme. The new iodine scheme contains a treatment of organic source gas emissions along with a new parameterisation of HOI and I2 emission from the ocean based on recent laboratory work. The model has been integrated at a horizontal resolution of 2.8o x 2.8o and is forced by ECMWF analyses for annual integrations.
We have used the model, coupled to a detailed size-resolved aerosol microphysics module, to study iodine chemistry in the troposphere. We will present comparisons with a range of surface, ship-borne, aircraft and satellite observations. The model reproduces observed surface CH3I distributions. Mixing ratios of other organic iodine compounds are small due to shorter lifetimes. Our simulations show the observed IO at Cape Verde in the Tropical East Atlantic cannot be reproduced with the measured organic iodine source fluxes alone and requires an additional iodine source, in agreement with other studies. Inclusion of the inorganic source improves the agreement, but the model still underestimates the largest observed OI, with HOI being the most abundant Iy species. Our simulations show iodine chemistry significantly perturbs tropospheric ozone. Emissions of organic iodine species result in a 17 Tg reduction in the troposphere ozone burden. The dominant iodine-driven ozone sink is the reaction of HO2 + IO (175 Tg O3 yr−1). |
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