edu.ucar.opensky::articles:11741 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T04:04:38.919894 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7r78fv0 Bromine and iodine chemistry in a global chemistry-climate model: Description and evaluation of very short-lived oceanic sources 2012-02-07T00:00:00Z publication https://n2t.org/ark:/85065/d7r78fv0 https://doi.org/10.5194/acp-12-1423-2012 Ordonez, C. author Lamarque, Jean-François author Tilmes, Simone author Kinnison, Douglas E. author Atlas, R. author Blake, D. author Sousa Santos, G. author Brasseur, Guy author Saiz-Lopez, A. author UCAR/NCAR - Library publisher The global chemistry-climate model CAM-Chem has been extended to incorporate an expanded bromine and iodine chemistry scheme that includes natural oceanic sources of very short-lived (VSL) halocarbons, gas-phase photochemistry and heterogeneous reactions on aerosols. Ocean emissions of five VSL bromocarbons (CHBr₃, CH2Br₂, CH₂BrCl, CHBrCl₂, CHBr₂Cl) and three VSL iodocarbons (CH₂ICl, CH₂IBr, CH₂I₂) have been parameterised by a biogenic chlorophyll-a (chl-a) dependent source in the tropical oceans (20° N-20° S). Constant oceanic fluxes with 2.5 coast-to-ocean emission ratios are separately imposed on four different latitudinal bands in the extratropics (20°-50° and above 50° in both hemispheres). Top-down emission estimates of bromocarbons have been derived using available measurements in the troposphere and lower stratosphere, while iodocarbons have been constrained with observations in the marine boundary layer (MBL). Emissions of CH₃I are based on a previous inventory and the longer lived CH₃Br is set to a surface mixing ratio boundary condition. The global oceanic emissions estimated for the most abundant VSL bromocarbons - 533 Gg yr⁻¹ for CHBr3 and 67.3 Gg yr⁻¹ for CH₂Br₂ -- are within the range of previous estimates. Overall the latitudinal and vertical distributions of modelled bromocarbons are in good agreement with observations. Nevertheless, we identify some issues such as the reduced number of aircraft observations to validate models in the Southern Hemisphere, the overestimation of CH2Br2 in the upper troposphere -- lower stratosphere and the underestimation of CH3I in the same region. Despite the difficulties involved in the global modelling of the shortest lived iodocarbons (CH₂ICl, CH₂IBr, CH₂I₂), modelled results are in good agreement with published observations in the MBL. Finally, sensitivity simulations show that knowledge of the diurnal emission cycle for these species, in particular for CH₂I₂, is key to assess their global source strength. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License None eng geoscientificInformation