A Study of DMS Oxidation in the Tropics: Comparison of Christmas Island Field Observations of DMS, SO2, and DMSO with Model Simulations |
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| Authors: | G Chen D D Davis P Kasibhatla A R Bandy D C Thornton B J Huebert A D Clarke B W Blomquist |
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| Institution: | (1) School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, U.S.A.;(2) School of Environment, Duke University, Durham, North Carolina, U.S.A.;(3) Department of Chemistry, Drexel University, Philadelphia, Pennsylvania, U.S.A.;(4) Department of Oceanography, University of Hawaii, Honolulu, U.S.A. |
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| Abstract: | This study reports comparisonsbetween model simulations, based on current sulfurmechanisms, with the DMS, SO2 and DMSOobservational data reported by Bandy et al.(1996) in their 1994 Christmas Island field study. For both DMS and SO2, the model results werefound to be in excellent agreement with theobservations when the observations were filtered so asto establish a common meteorological environment. Thisfiltered DMS and SO2 data encompassedapproximately half of the total sampled days. Basedon these composite profiles, it was shown thatoxidation of DMS via OH was the dominant pathway withno more than 5 to 15% proceeding through Cl atoms andless than 3% through NO3. This analysis wasbased on an estimated DMS sea-to-air flux of 3.4 ×109 molecs cm-2 s-1. The dominant sourceof BL SO2 was oxidation of DMS, the overallconversion efficiency being evaluated at 0.65 ± 0.15. The major loss of SO2 was deposition to theocean's surface and scavenging by aerosol. Theresulting combined first order k value was estimated at 1.6 × 10-5 s-1. In contrast to the DMSand SO2 simulations, the model under-predictedthe observed DMSO levels by nearly a factor of 50. Although DMSO instrument measurement problems can notbe totally ruled out, the possibility of DMSO sourcesother than gas phase oxidation of DMS must beseriously considered and should be explored in futurestudies. |
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| Keywords: | dimethyl sulfide sulfur dioxide DMS oxidation SO2 wet/dry deposition |
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