Tropospheric ozone in the tropical Atlantic is an important part of the global ozone budget that is not well understood. The ozone system in the region is complex: Biomass burning, lightning, wind transport, stratospheric injection, and inter-hemispheric exchange have all been cited as sources and sinks. For such a complex system, there is remarkably little in-situ data. Only a handful of cruises have taken data in the region over the last 20 years, 3 of which have been AEROSE missions. The AEROSE missions have been a series of cruises in the tropical Atlantic focused on researching the characteristics and influences of the Saharan air layer (SAL) and the Saharan dust it frequently carries.

During May 2007, a series of meteorological soundings was taken in the tropical Atlantic Ocean from the NOAA vessel Ronald H. Brown as part of the AEROSE-III field campaign. Seventeen electrochemical cell (ECC) ozone sondes, each interfaced with a Vaisala RS92 radiosonde, were launched. The first 8 soundings were taken once a day, along a transect following 23 degrees West Longitude, from 4 degrees North Latitude to 20 degrees North Latitude. The remaining 9 were taken on a NW-bearing transect from 20 N, 28 W to 25.5 N, 70 W. The ECC ozone sonde measures ozone concentration via current generated by a chemical reaction between ozone and potassium-iodine solution.

The data over the S-N transect reveals three high-ozone events on May 15, 17, and 19, each with ozone concentrations exceeding 100 ppbv. A study is in progress to reveal the ozone sources for each of these events. Preliminary results are presented in this paper as well as general characterization of tropospheric ozone concentrations that were observed throughout the cruise.