Extended Abstract (128K)14.1
Atmospheric methane at Suva, Fiji: The impact of tropical meteorology
David Lowe, National Institute of Water and Atmospheric Research, Wellington, New Zealand; and T. Bromley, B. Allan, and K. Koshy
Atmospheric methane mixing ratios in the extra tropical southern hemisphere reveal regular seasonal cycles with peak-to-peak amplitude of about 40ppb. These are superimposed on a secular trend with a growth rate that has varied from more than 15 ppb/yr to about zero during the last 10 years. The seasonal cycles are driven by regular annual changes in the production of the atmospheric hydroxyl radical, the chemical sink for atmospheric methane, and the secular trend is modulated by variations in the balance of its sources and sinks. In 1994 we began a series of measurements of atmospheric methane mixing and stable isotopic ratios at a surface site in Suva, Fiji (18°S). These data show large variability when compared to similar data collected at Baring Head, New Zealand (41°S). We attribute the differences in the datasets to the impact of tropical meteorology at the Suva site. For example in 1999, during a cold phase ENSO event, the South Pacific Convergence zone was located south of the Suva site and we observed methane mixing ratio and isotopic values representative of northern hemisphere air. In this work we present methane data from the Suva and other southern hemisphere sites and examine the influence of ENSO events and the movement of the South Pacific and Inter tropical convergence zones on these values.
Session 14, Atmospheric Chemistry in the Southern Hemisphere
Thursday, 27 March 2003, 9:00 AM-12:00 PM
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