Abstract
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 (CH 2ICl, CH2IBr, CH2I2) have been parameterised by a biogenic chlorophyll-α (chl-α) 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 CHBr 3 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, CH 2I2), 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.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1423-1447 |
| Number of pages | 25 |
| Journal | Atmospheric Chemistry and Physics |
| Volume | 12 |
| Issue number | 3 |
| DOIs | |
| State | Published - 2012 |
Fingerprint
ASJC Scopus subject areas
- Atmospheric Science
Cite this
Bromine and iodine chemistry in a global chemistry-climate model : Description and evaluation of very short-lived oceanic sources. / Ordóñez, C.; Lamarque, J. F.; Tilmes, S.; Kinnison, D. E.; Atlas, Elliot L; Blake, D. R.; Sousa Santos, G.; Brasseur, G.; Saiz-Lopez, A.
In: Atmospheric Chemistry and Physics, Vol. 12, No. 3, 2012, p. 1423-1447.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Bromine and iodine chemistry in a global chemistry-climate model
T2 - Description and evaluation of very short-lived oceanic sources
AU - Ordóñez, C.
AU - Lamarque, J. F.
AU - Tilmes, S.
AU - Kinnison, D. E.
AU - Atlas, Elliot L
AU - Blake, D. R.
AU - Sousa Santos, G.
AU - Brasseur, G.
AU - Saiz-Lopez, A.
PY - 2012
Y1 - 2012
N2 - 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 (CH 2ICl, CH2IBr, CH2I2) have been parameterised by a biogenic chlorophyll-α (chl-α) 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 CHBr 3 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, CH 2I2), 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.
AB - 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 (CH 2ICl, CH2IBr, CH2I2) have been parameterised by a biogenic chlorophyll-α (chl-α) 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 CHBr 3 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, CH 2I2), 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.
UR - http://www.scopus.com/inward/record.url?scp=84860641358&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84860641358&partnerID=8YFLogxK
U2 - 10.5194/acp-12-1423-2012
DO - 10.5194/acp-12-1423-2012
M3 - Article
AN - SCOPUS:84860641358
VL - 12
SP - 1423
EP - 1447
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
SN - 1680-7316
IS - 3
ER -