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Speaker: | Herman Sievering, U.of Colorado, Boulder, CO |
Date/Time: | Tuesday, May 5, 2009 10:00AM |
Location: | NOAA David Skaggs Research Center, Room 2A305 |
Title: | Biogenic Matter Influences on SO2 Oxidation and Removal from the Marine Boundary Layer and its Role in Over Ocean CCN Aerosol Characterization |
Marine boundary layer (MBL) aerosol measurements have shown that O3-oxidation of SO2 in seasalt aerosols plays an important role in global MBL sulfur cycling and budgets. Field studies at Baring Head, NZ and, recently, at Cape Grim, AU show that biogenic matter from upwind surface waters' primary productivity (PP) not only provides alkalinity to "feed" this seasalt O3-oxidation of SO2 but also produces submicron biogenic-derived aerosols that are active CCN. At Baring Head, substantial upwind PP provided enough alkalinity for O3-oxidation to remove all DMS-derived SO2 back to ocean surface waters. Model estimates of effective SO2 dry deposition velocities (effVd), once accounting for removal in seasalt aerosols, show effVd is 3- to 10-times that of direct SO2 gaseous dry deposition velocities. These large effVd indicate that DMS-derived, submicron non-seasalt sulfate aerosols contribute far less to cloud condensation nuclei (CCN) in the MBL than previously thought.
Cape Grim aerosol sampling took place at 110 m asl (completely removed from local soil and seaspray aerosols) with upwind ocean surface waters' PP at global ocean mean PP levels. Ratios of submicron aerosol excess K+ to excess Ca++ (beyond bulk seawater K+ and Ca++) indicate that 50-500 nm aerosols have very different characteristics when upwind PP is or is not active. During periods of much reduced upwind PP (e.g., winter), fragmented plankton debris dominates the surface waters biogenic matter contribution to these CCN size aerosols. During PP active periods, our ion data suggest several biogenic matter sources produce 50-500 nm aerosols. Electron microscope analysis of Cape Grim aerosols show the large majority of 10-100 nm aerosols to be a mix of fragmented marine organisms coated with highly surface active polymer gels, or gels themselves; thus active CCN. Very few <100 nm seasalt or ammonium sulfate aerosols were found. The biogenic matter aerosol source has important consequences for the concentration and character of CCN in the MBL.
Co-authors: J. Cainey (Cape Grim Baseline Stn., AU), M. Harvey (NIWA, NZ), M. Keywood (CSIRO, AU), C. Leck (Stockholm U.) and R. von Glasow (U. of East Anglia, UK)
Speaker: | Dave Hofmann, CIRES, ESRL/GMD |
Date/Time: | Tuesday, May 19, 2009 03:30PM |
Location: | Multi-purpose Room (GC-402) David Skaggs Research Center (DSRC) |
Title: | Increase in Background Stratospheric Aerosol Since 2000: Is it Related to Increased Coal Burning in China? |
Speaker: | Robert J. Charlson, Professor, Department of Atmospheric Sciences and Department of Chemistry, University of Washington, Seattle, WA |
Date/Time: | Thursday, June 18, 2009 03:30PM |
Location: | Multi-purpose Room (GC-402), David Skaggs Research Center (DSRC), NOAA Building, DOC Boulder Campus |
Title: | Sulfate aerosol effects on climate: The observational pathway to the first estimates of forcing |