HR: 15:20h
AN: A43F-07 INVITED    [Abstracts]
TI: An Overview of Polar HOx Chemistry and Potential Bromine Chemistry Impact.
AU: * CHEN, G
EM: gao.chen@nasa.gov
AF: NASA Langley Research Center, Mail Stop 401B, Hampton, VA 23693, United States
AU: HUEY, L G
EM: greg.huey@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst St., Atlanta, GA 30332, United States
AU: DIBB, J E
EM: jack.dibb@nasa.gov
AF: Unversity of New Hampshire, Morse Hall,39 College Road, Durham, NH 03824, United States
AU: OLSON, J R
EM: jennifer.r.olson@nasa.gov
AF: NASA Langley Research Center, Mail Stop 401B, Hampton, VA 23693, United States
AU: CRAWFORD, J H
EM: james.h.crawford@nasa.gov
AF: NASA Langley Research Center, Mail Stop 401B, Hampton, VA 23693, United States
AU: SJOSTED, S
EM: ssjosted@chem.utoronto.ca
AF: University of Toronto, 86 St. George Street, Toronto, ON M5S3H6, Canada
AU: Tanner, D
EM: david.tanner@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst St., Atlanta, GA 30332, United States
AU: Davis, D D
EM: douglas.d.davis@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst St., Atlanta, GA 30332, United States
AB: It is now well recognized that the snow-air exchange is a critical component of polar photochemical cycles. Observed large snow to air gradients as well as elevated levels of many reactive species, e.g., NO, CH2O, have inspired intense studies on the snow/firn air chemical processes and the impact of snow emissions on the atmospheric chemistry above the snow covered surface. The first observations of OH at the South Pole (SP) revealed levels comparable to those recorded in the tropical marine boundary layer. Modeling interpretive analysis later attributed these high OH levels to snow emissions of CH2O, H2O2, and NO, leading to enhanced HOx (OH + HO2) sources. The enhanced oxidation capacity, in turn, can rapidly oxidize NOx into HNO3 and HO2NO2, which deposit back to the snow surface. During summer of 2003, the HO and HO2 were simultaneously measured at Summit, Greenland for the first time. This rich data set allowed a more comprehensive analysis of arctic HOx chemistry. Modeling analysis suggests that snow emissions are an important Summit HOx source, but unlike the SP case, they were not dominant one. While model can well reproduce the observed HOx levels and diurnal variations when constrained by measured precursors, they typically over-predicts the HO2/OH ratio by about a factor of 2. In an extreme case, model overprediction is up to a factor of 8. The latter case involved high wind speed. Trajectory analysis suggests that the airmass was brought from the coast region within 2 days. This raises the speculation about the role of BrO. In light of Summit BrO observations during the summer of 2007, two model simulation scenarios will be discussed as related to the sensitivity of Summit HOx and other important photochemical species to BrO levels. The first one involves a fixed BrO level, while the second simulates the effect of a pulse high BrO injection into the summertime Summit environment.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting