2024-03-29T10:03:04Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/339282022-11-17T02:08:08Zhdl_2115_20051hdl_2115_144Ozonesonde observations at Christmas Island (2°N, 157°W) in the equatorial central PacificTakashima, H.Shiotani, M.Fujiwara, M.Nishi, N.Hasebe, F.ozonetropical tropopause layerequatorial central Pacific452Ozone and water vapor observations have been conducted at Christmas/Kiritimati Island (2 degrees N, 157 degrees W) in the equatorial central Pacific as a part of the Soundings of Ozone and Water in the Equatorial Region (SOWER)/Pacific mission. We launched 33 ozonesondes and 33 chilled-mirror hygrometers in nine observation campaigns from 1999 to 2003 for various seasons. We found that ozone concentrations at Christmas Island are low in the whole troposphere (similar to 10-35 ppbv), particularly in the marine boundary layer (MBL). Ozone variation is small throughout the year compared with other tropical stations, though annual and interannual variations of meteorological fields are large over the equatorial central Pacific. Just below the tropopause, during the August 2002 campaign, we observed substantially reduced ozone concentrations (<10 ppbv) similar to those found in the MBL, which are maintained at least for the observation period. From meteorological conditions, we found that air mass was advected from the Inter-Tropical Convergence Zone (ITCZ), located to the north of Christmas Island, in accordance with the northeasterly wind that is only observed during northern summer in the upper troposphere. The origin of air mass is supposed to be from the MBL in the ITCZ.American Geophysical UnionJournal Articleapplication/pdfhttp://hdl.handle.net/2115/33928https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/33928/1/X20080201.pdf0148-0227Journal of Geophysical Research113d10D101122008-05-30enginfo:doi/10.1029/2007JD009374An edited version of this paper was published by AGU. Copyright © 2008 American Geophysical Union.author