HR: 17:40h
AN: A44B-05    [Abstracts]
TI: Modeling the Sources of Organic Carbon Aerosol in the Free Troposphere
AU: * Heald, C L
EM: heald@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Jacob, D J
EM: djj@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Park, R J
EM: rjp@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Turquety, S
EM: stu@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Hudman, R C
EM: rch@io.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Weber, R J
EM: rweber@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Georgia Institute of Technology, Atlanta, GA 30332 United States
AU: Peltier, R
EM: rpeltier@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Georgia Institute of Technology, Atlanta, GA 30332 United States
AU: Sullivan, A
EM: amy.sullivan@eas.gatech.edu
AF: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Georgia Institute of Technology, Atlanta, GA 30332 United States
AU: Russell, L M
EM: lmrussell@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla, CA 92093
AU: Huebert, B J
EM: huebert@soest.hawaii.edu
AF: Department of Oceanography, University of Hawai`i at Manoa, 1000 Pope Road, Honolulu, HI 96822 United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Mail Code 210-41, Pasadena, CA 91125 United States
AU: Liao, H
EM: hong@its.caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Mail Code 210-41, Pasadena, CA 91125 United States
AB: Two recent aircraft campaigns have provided extensive measurements of organic carbon (OC) aerosol mass concentrations in the free troposphere, and reveal values considerably larger than presently simulated by global chemical transport models (CTMs). The ACE-Asia campaign in spring of 2001 off the coast of Japan found concentrations averaging 4 μg m-3 STP in the 2-6.5 km column with little vertical gradient. These concentrations are 10-100 times higher than computed with the GEOS-Chem CTM including a standard 2-product simulation of secondary organic aerosol (SOA) formation from biogenic sources based on empirical fits to smog chamber data. The same CTM reproduces successfully the observed vertical profiles of sulfate and elemental carbon aerosols, which indicate sharp decreases from the boundary layer to the free troposphere due to wet scavenging. Our results suggest either that lifting of OC aerosols from the boundary layer takes place with unexpectedly little scavenging, or that a large sustained source of SOA is present in the free troposphere. More recent measurements of water-soluble OC aerosol made during the ICARTT campaign over the eastern U.S. in summer 2004, also show high concentrations, averaging 1 μ-g m-3 STP in the free troposphere up to 6 km. We will present GEOS-Chem simulations of the ACE-Asia and ICARTT periods examining different possible mechanisms to account for the high observed OC aerosol concentrations in the free troposphere.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005