HR: 0830h
AN: A51A-07    [Abstracts]
TI: Long-Term Observations of BrO at Lauder, New Zealand and Arrival Heights, Antarctica
AU: * Kreher, K
EM: k.kreher@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Johnston, P V
EM: p.johnston@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Wood, S W
EM: s.wood@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Struthers, H
EM: h.struthers@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Thomas, A
EM: a.thomas@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Smale, D
EM: d.smale@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Bodeker, G E
EM: g.bodeker@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Connor, B J
EM: b.connor@niwa.co.nz
AF: National Institute of Water and Atmospheric Research, Lauder, Private Bag 50061 , Omakau, 9182 New Zealand
AU: Schofield, R
EM: RobynSchofield@noaa.gov
AF: NOAA Aeronomy Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Dix, B
EM: barbara.dix@iup.uni-heidelberg.de
AF: Institute for Environmental Physics, University of Heidelberg Im Neuenheimer Feld 229, Heidelberg, 69120 Germany
AU: Friess, U
EM: uf5@leicester.ac.uk
AF: Department of Physics and Astronomy, University of Leicester University Road, Leicester, LE1 7RH United Kingdom
AU: Oltmans, S J
EM: Samuel.J.Oltmans@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Chipperfield, M P
EM: martyn@env.leeds.ac.uk
AF: School of the Environment, University of Leeds, Leeds, United Kingdom
AB: As part of the Network for Detection of Stratospheric Change (NDSC) ground-based measurements of BrO (bromine oxide) have been made using zenith-sky UV/vis absorption spectroscopy at Lauder, New Zealand (45°S, 170°E), and at Arrival Heights, Antarctic (78°S, 167°E). These BrO column measurements have been made continuously since 1995 and are the only two decadal Southern Hemisphere ground-based data sets. A knowledge of long-term changes in BrO is important since in the lower stratosphere during winter and spring the ClO+BrO ozone loss cycle can be as important as the ClO dimer cycle (up to 40% each) over the Antarctic, and can account for up to 20% of ozone loss between 40°S and 50°S (1). Furthermore, while stratospheric concentrations of chlorine containing compounds are expected to decrease in the future, concentrations of bromine containing compounds, and in particular methyl bromide (CH₃Br), are changing little. Therefore, compared to ClO, the relative contribution of BrO to ozone depletion could increase in the future. To this end we have analyzed our BrO column measurements at both locations for long-term variability and trends. Recent studies have shown that although existing models are able to approximately predict the amount of BrO in the atmosphere, the distribution of BrO in the stratosphere-troposphere layers could be misrepresented and the inorganic bromine (Br_y) at and above the tropopause could be 4-8 ppt greater than currently assumed in models used in past ozone trend assessments. Intercomparisons between model results and measurements provide a very sensitive test of the model and can highlight model inadequacies. We have therefore compared our measurements with output from two models to assess the ability of the models to reproduce the long-term trends and variability in our data. In polar regions, BrO concentrations in the lower troposphere can be rapidly elevated through non-linear chemistry thought to involve sea-salt particles deposited onto the sea-ice; so called `BrO explosion events'. To better diagnose these events and their impact on tropospheric ozone at Arrival Heights, in 1999 the zenith-sky measurements were complemented with measurements made using a multi-axis viewing geometry. In addition, during spring 2002, direct-sun BrO measurements were made. The latter two types of observation provide more accurate information on the tropospheric component of the BrO column. All three BrO data sets were investigated for sudden strong increases in BrO and concomitant decreases in surface ozone typical of a BrO explosion event. References (1) Lee, A.M., R.L. Jones, I. Kilbane-Dawe, and J.A. Pyle, Diagnosing ozone loss in the extratropical lower stratosphere, Journal of Geophysical Research, 107 (D11), 10.1029/2001JD000538, 2002.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly