Comparison of Model Evaluated and Measured Profiles for Sulfur Species as Observed During ACE-1

D D Davis , G Chen and B Burgess
(School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332; 404-894-9565; e-mail: dd16@prism.gatech.edu)

A Bandy and D Thorton
(both at: Department of Chemistry, Drexel University, Philadelphia, PA 19104)

F L Eisele, D J Tanner, and A Jefferson
(ACD/NCAR, P.O. Box 3000, Boulder, CO 80307)

To be discussed are sulfur model simulation results from two representative flights from the ACE-1 (Aerosol Characterization Experiment) program (Nov-Dec, 1995).The box model used in these simulations consisted of two modules: a basic HOx-NOx-CH₄/NMHC chemistry module used to generate diurnal profiles of OH and NO₃, and a sulfur chemistry module which used these OH and NO₃ profiles to generate time dependent profiles for DMS, SO₂, DMSO, DMSO₂, MSIA, MSA, and H₂SO₄. The DMS flux used in the model simulation was derived from three independent methods: marine DMS observations, aircraft boundary layer DMS gradient measurements, and marine boundary layer DMS mass conservation based on photochemical destruction (e.g. reactions with OH and NO₃) and vertical transport processes. The vertical transport processes were parameterized in the sulfur module similar to that described by Lenschow et al. (1986). The sulfur mechanism employed is that described previously by Davis et al.,(1996). Observational data used to constrain the sulfur model by defining several critical branching ratios in the mechanism consisted of DMS, SO₂, MSA, and H₂SO₄.