edu.ucar.opensky::articles:7485 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T15:41:32.346718 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d78p60tj Concentrations and sources of organic carbon aerosols in the free troposphere over North America 2006-12-12T00:00:00Z publication https://n2t.org/ark:/85065/d78p60tj https://doi.org/10.1029/2006JD007705 Heald, C. author Jacob, D. author Turquety, S. author Hudman, Rynda C. author Weber, R. author Sullivan, A. author Peltier, R. author Atlas, Elliot author De Gouw, J. author Warneke, C. author Holloway, J. author Neuman, J. author Flocke, Frank M. author Seinfeld, J. author UCAR/NCAR - Library publisher Aircraft measurements of water-soluble organic carbon (WSOC) aerosol over NE North America during summer 2004 (ITCT-2K4) are simulated with a global chemical transport model (GEOS-Chem) to test our understanding of the sources of organic carbon (OC) aerosol in the free troposphere (FT). Elevated concentrations were observed in plumes from boreal fires in Alaska and Canada. WSOC aerosol concentrations outside of these plumes average 0.9 ± 0.9 μg C m⁻³ in the FT (2-6 km). The corresponding model value is 0.7 ± 0.6 μg C m⁻³, including 42% from biomass burning, 36% from biogenic secondary organic aerosol (SOA), and 22% from anthropogenic emissions. Previous OC aerosol observations over the NW Pacific in spring 2001 (ACE-Asia) averaged 3.3 ± 2.8 μg C m⁻³ in the FT, compared to a model value of 0.3 ± 0.3 μg C m⁻³. WSOC aerosol concentrations in the boundary layer (BL) during ITCT-2K4 are consistent with OC aerosol observed at the IMPROVE surface network. The model is low in the boundary layer by 30%, which we attribute to secondary formation at a rate comparable to primary anthropogenic emission. Observed WSOC aerosol concentrations decrease by a factor of 2 from the BL to the FT, as compared to a factor of 10 decrease for sulfate, indicating that most of the WSOC aerosol in the FT originates in situ. Despite reproducing mean observed WSOC concentrations in the FT to within 25%, the model cannot account for the variance in the observations (R = 0.21). Covariance analysis of FT WSOC aerosol with other measured chemical variables suggests an aqueous-phase mechanism for SOA generation involving biogenic precursors. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2006 American Geophysical Union. None eng geoscientificInformation