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Science Questions

  1. What are the emissions of aerosol, aerosol precursors and greenhouse gases in the SE U.S.?
    • How well do inventories represent the urban emissions of organic aerosol, black carbon NOx, volatile organic compounds (VOCs), SO2 and greenhouse gases?
    • How well do inventories represent the emissions of aerosol precursors from point sources, such as coal-fired power plants?
    • How well do inventories represent biogenic VOC emissions?
    • How significant are the emissions from biomass burning?

    Approach: To answer these questions, the NOAA WP-3D will make flight legs downwind from urban and point sources of trace gases and aerosol, and measure the mixing ratios of biogenic VOCs during regional surveys.

  2. What is the composition and distribution of aerosol in the SE U.S.?
    • What is the relative importance of sulfate, organics and other chemical components?
    • How does this change with altitude?

    Approach: Average mass loadings of aerosol will be determined from flights in specific regions and under specific meteorological conditions (pre- and post-frontal), and compared to models.

  3. What are the formation mechanisms of secondary species (ozone, sulfate and organics) in the SE U.S.?
    • What do the vertical profiles of sulfate and of organic aerosol reveal about their respective sources?
    • How do biogenic emissions affect ozone production by modifying the processing and export efficiency of NOx emissions through organic nitrates? What is the role of terpenes in global oxidation?
    • How important is organic aerosol and ozone formation from nighttime oxidation of biogenic VOCs?
    • How important is the formation of sulfate and organics from aqueous-phase processes?

    Approach: What are the significant precursors of organic aerosol? What role do anthropogenic emissions play in the formation of organic aerosol from biogenic precursors? To answer these questions, the NOAA WP-3D will follow air masses from different sources (urban, power plants, forests) as they are processed during the day, at night, with and without the presence of biogenic emissions, and through cumulus and shallow convective clouds.

  4. Which deposition processes are critical for determining atmospheric concentrations of aerosol, ozone and NOy?
    • What deposition processes (dry, and in-cloud or below-cloud wet deposition) are controlling aerosol lifetimes?
    • What techniques and instrumentation can be deployed in SOAS to quantify aerosol, ozone and NOy deposition?

    Approach: The rate at which species are lost by deposition can be estimated using measurements of different hydrocarbon species, which are removed at different rates based on their reactivity with hydroxyl radicals.

  5. What are the climate-relevant properties of aerosol in the SE U.S.?
    • What are the extinction, absorption and CCN properties of aerosol from primary and secondary sources? How do these depend on the high humidity in the SE U.S.?
    • What fraction of the organic aerosol is natural versus controlled by anthropogenic emissions?
    • How will this change in the future as a result of warming and changes in anthropogenic emissions?
    • Given that black carbon is co-emitted with other species, will controlling specific BC sources have a net warming or cooling effect?

    Approach: Aerosol extinction, absorption and cloud nucleating properties will be measured from the aircraft for different aerosol types. Correlating the variability in aerosol with inert tracers for different emission sources, e.g. carbon monoxide (CO) for urban emissions, acetonitrile for biomass burning emissions, will help to describe the fraction of aerosol that is controlled by anthropogenic emissions.