Publication Abstracts

Bell et al. 2002

Bell, N., L. Hsu, D.J. Jacob, M.G. Schultz, D.R. Blake, J.H. Butler, D.B. King, J.M. Lobert, and E. Maier-Reimer, 2002: Methyl iodide: Atmospheric budget and use as a tracer of marine convection in global models. J. Geophys. Res., 107, no. D17, 4340, doi:10.1029/2001JD001151.

We simulate the oceanic and atmospheric distribution of methyl iodide (CH3I) with a global 3-D model driven by assimilated meteorological observations from the Goddard Earth Observing System (GEOS) of the NASA Data Assimilation Office (DAO) and coupled to an oceanic mixed layer model. A global compilation of atmospheric and oceanic observations is used to constrain and evaluate the simulation. Seawater CH3I(aq) in the model is produced photochemically from dissolved organic carbon (DOC), and is removed by reaction with Cl- and emission to the atmosphere. The net oceanic emission to the atmosphere is 210 Gg/yr. Small terrestrial emissions from rice paddies, wetlands, and biomass burning are also included in the model. The model captures 40% of the variance in the observed seawater CH3I(aq) concentrations. Simulated concentrations at midlatitudes in summer are too high, perhaps because of a missing biological sink of CH3I(aq). We define a marine convection index (MCI) as the ratio of upper tropospheric (8-12 km) to lower tropospheric (0-2.5 km) CH3I concentrations averaged over coherent oceanic regions. The MCI in the observations ranges from 0.11 over strongly subsiding regions (southeastern subtropical Pacific) to 0.40 over strongly upwelling regions (western equatorial Pacific). The model reproduces the observed MCI with no significant global bias (offset of only + 11%) but accounts for only 15% of its spatial and seasonal variance. The MCI can be used to test marine convection in global models, complementing the use of radon-222 as a test of continental convection.

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BibTeX Citation

  author={Bell, N. and Hsu, L. and Jacob, D. J. and Schultz, M. G. and Blake, D. R. and Butler, J. H. and King, D. B. and Lobert, J. M. and Maier-Reimer, E.},
  title={Methyl iodide: Atmospheric budget and use as a tracer of marine convection in global models},
  journal={J. Geophys. Res.},

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RIS Citation

ID  - be02000x
AU  - Bell, N.
AU  - Hsu, L.
AU  - Jacob, D. J.
AU  - Schultz, M. G.
AU  - Blake, D. R.
AU  - Butler, J. H.
AU  - King, D. B.
AU  - Lobert, J. M.
AU  - Maier-Reimer, E.
PY  - 2002
TI  - Methyl iodide: Atmospheric budget and use as a tracer of marine convection in global models
JA  - J. Geophys. Res.
VL  - 107
IS  - D17
SP  - 4340
DO  - 10.1029/2001JD001151
ER  -

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