14.5
Variability in ozone in the tropical troposphere from the SHADOZ (Southern Hemisphere ADditional OZonesondes) network
Anne M Thompson, NASA/GSFC, Greenbelt, MD; and J. C. Witte, F. J. Schmidlin, S. J. Oltmans, V. W. J. H. Kirchhoff, G. J. R. Coetzee, F. Posny, T. Ogawa, J. P. F. Fortuin, and H. Kelder
The first view of zonal, seasonal and interannual tropospheric variability from sondes is provided by a 12-site record from the Southern Hemisphere ADditional OZonesondes (SHADOZ) network: http://code916.gsfc.nasa.gov/Data_services/shadoz. Observations since 1998 have been made over Ascension Island; Nairobi and Malindi, Kenya; Irene, South Africa; La Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. The tropopause is lower in September-October-November than in March-April-May, when ozone is a minimum at most SHADOZ stations. A zonal wave-one pattern (referring to ozone mixing ratios greater over the Atlantic and adjacent continents than over the Pacific and eastern Indian Ocean), persists all year. The wave, predominantly in the troposphere and with variable magnitude, appears to be due to general circulation - with subsidence over the Atlantic and frequent deep convection over the Pacific and Indian Ocean. The variability of deep convection - most prominent at Java, Fiji, Samoa and Natal - is explored in time-vs-altitude ozone curtains. One of the most distinctive features of SHADOZ tropospheric ozone is great variability, e.g. a factor of three in column ozone at 8 stations. Seasonal and monthly means may not be robust quantities because statistics are frequently not Gaussian, even at sites that are always in tropical air. This has implications for models and satellite retrievals. They should be evaluated on their capability for reproducing tropospheric variability and fine-structure. A 1999-2001 ozone record from Paramaribo, Surinam (6N, 55W), the only northern tropical site in SHADOZ, shows a marked contrast to southern ozone because Surinam is often north of the ITCZ. To further improve the tropospheric ozone climatology for models and satellite retrievals requires extension of the network to more northern hemisphere tropical locations.
Session 14, Atmospheric Chemistry in the Southern Hemisphere
Thursday, 27 March 2003, 9:00 AM-12:00 PM
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