HR: 14:20h
AN: A43F-03    [Abstracts]
TI: A Re-assessment of Nitrogen Recycling on the Antarctic Plateau
AU: * Davis, D D
EM: douglas.davis@eas.gatech.edu
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA 30332,
AU: Chen, G
AF: NASA Langley Research Center, Atmospheric Sciences Division, Hampton, VA 23681,
AU: Neff, W
EM: william.neff@noaa.gov
AF: NOAA, Earth System Research Laboratory, Boulder, CO 80305,
AB: Since the initial finding some 8-9 years ago that polar regions are not simply chemical graveyards, it has become increasing apparent that the physical and chemical processes taking place in the snowpack are quite complex. With regard to the specific snow emission species NOx, nowhere have atmospheric levels been observed to be higher than those seen on the Antarctic plateau with median values of NO/NOx typically being one order of magnitude higher than at other sites investigated. Several field studies, particularly those focused on the South Pole (SP) region, have been carried out with the purpose of gaining an improved understanding why this is so. Factors that have thus far been identified as contributing to this large difference include: 1) 24 hours of continuous solar radiation during the spring/summer months while also frequently experiencing the onset of shallow planetary boundary layer (PBL) depths; 2) a geographical location that is near a convergence point for air drainage from the central high plateau; and 3) extremely low average temperatures (e.g., low H2O levels) on the plateau which lead to a very weak primary source of HOx radicals. The latter condition, in particular, leads to NOx being a major controller of HOx radical levels. Thus, when in excess of ~250 pptv, the NOx lifetime increases with further increases in NOx, leading to a further ramping up of the NOx concentration. What has not yet been established is whether there is still a fourth factor which is related to differences in snow emission rates of NOx at the different sites. To be presented are new field data, the results of which strongly suggest that the plateau has the unique ability to recycle reactive nitrogen more than once within a given spring/summer season, thus enhancing the overall nitrogen emission rate.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting