9420175 Bradshaw This research will focus on characterizing ammonia's (NH3) impact on the tropospheric chemistry within the remote marine atmosphere through the quantitative measurement of gas phase NH3, "total" NH3 (i.e. gaseous plus particulate), and nitric oxide (NO) on board the NSF/NCAR C-130 aircraft during the 1995 Southern Hemisphere Marine Aerosol Characterization Experiment (ACE-1). This effort will seek to address NH3's role within the primary ACE-1 program objective of determining the key physical and chemical processes controlling the formation and fate of aerosols and how these processes affect the number size distribution, the chemical composition, and the optical and cloud nucleating properties of these particles. For a few parts-per-trillion levels of NH3 that are anticipated over the ACE- 1 study regions, the Georgia Tech advanced photofragmentation laser-induced fluorescence (PF/LIF) sensor will be used to acquire high precision ( 10%, 2s) data with sufficient spatial resolution to enable a detailed characterization of the small spatial scale atmospheric inhomogeneities that are thought to give rise to bursts in condensation nuclei (CN) production. These unprecedented measurement capabilities will produce data capable of yielding new insights into NH3's role in controlling the development of CN and the growth and activation of cloud condensation nuclei (CCN). In conjunction with other ACE-1 measurements, this project should provide a unique perspective of the relative contributions that binary and ternary nucleation processes make toward controlling the rate of new particle production in the remote atmosphere. This investigation will also provide the atmospheric community with needed information of the spatial distribution of NH3 within the troposphere over remote marine environments. This large spatial scale survey will also provide the basis for the first quantitative assessment of NH3's role as possible source of nitrogen oxides (N0x) i n the remote troposphere.
