Measurements of tracers for marine organic carbon chemistry at interfaces: relevance for the oxidative capacity of the tropical troposphere

Speaker: Rainer Volkamer and the TORERO team, University of Colorado at Boulder

When: Wednesday, February 6, 2013, 3:30 p.m. Mountain Time
Location: Room 2A305, DSRC (NOAA Building), 325 Broadway, Boulder
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Oceans cover 70% of the Earth surface, and the amount of dissolved organic carbon (DOC) contained in the world's oceans is comparable to that of atmospheric CO2. Yet oceans are currently believed to be a receptor for organic carbon that is emitted over land. Recent our observations of very short-lived and very water soluble oxygenated hydrocarbons, like glyoxal, in the remote marine boundary layer (MBL) above the Pacific Ocean (Sinreich et al., 2010, ACP) remain as of yet unexplained by atmospheric models. Organic carbon is relevant in the atmosphere because it influences the reactive chemical removal pathways of climate active gases (i.e., ozone, methane, dimethyl-sulfide), and can modify aerosols (e.g., secondary organic aerosol, SOA). In the free troposphere atmospheric models predict even lower glyoxal than in the remote MBL; models remain largely untested in the free troposphere for lack of observations. Satellite retrievals of glyoxal provide valuable global data sets, but in lack of vertically resolved observations, and uncertain source mechanisms these maps remain qualitative over oceans. The Tropical Ocean tRoposphere Exchange experiment TORERO (Jan/Feb 2012, PI: Volkamer) deployed an innovative payload of optical spectroscopic-, mass spectrometric-, and remote sensing instruments aboard the NSF/NCAR GV aircraft (HIAPER), and aboard a NOAA ship to measure halogen oxide radicals, very short lived halogen species (VSLS) precursors, oxygenated hydrocarbons, and volatile organic compounds (some 50+ species), aerosol size distributions, optical properties, and photolysis frequencies over the full tropospheric air column (0-15km altitude) between 40N to 40S latitude over the eastern tropical Pacific Ocean. This talk describes selected TORERO measurements, and exploits unique properties of organic tracer molecules (i.e., volatility, solubility), as well as their vertical distributions to test our process level understanding of the sources and sinks of organic carbon in the tropical atmosphere. The implications on oxidative capacity (OH-, Br-, I- radical abundance) are assessed with a particular focus on the tropical free troposphere, where most of tropospheric ozone mass resides, 60-80% of the global methane destruction occurs, and mercury oxidation rates are accelerated at low temperatures.