Chemistry of tropospheric ozone over the tropical Pacific

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Tropospheric ozone (O_3) is one of the important greenhouse gases. This fact was a common knowledge in the research field of atmospheric radiation, but it has been recently re-focused in the atmospheric environmental science. Atmospheric ozone also plays an important role in controlling a number of reactions. For example, photolysis of ozone by ultraviolet radiation leads to the production of OH,which scavenges many important trace gases including CH _4, HCFCs (hydrochlorofluorocarbons) and CO.NASA conducted the aircraft mission PEM-Tropics, which was aimed to study tropospheric chemistry over tropical and southern hemispheric Pacific Ocean. Two kinds of aircraft were operated to measure reactive nitrogen and other precursor species. Observations were made over the west coast of south America and over the central Pacific near Hawaii and New Zealand in September and October, 1996. Aircraft measurements were made successfully and the data is being processed. The finalized data will be archived in the NASA data base. Air descends over south American region during this period due to Walker circulation. Low levels of H_2O and high levels of O_3 observed in the upper troposphere is consistent with this transport. We made cooperated efforts with scientists of University of Michigan for this program. Systematic analyzes are to be made using the Archived data available in near future.We made site visit to Indonesia in August 1996 in order to prepare for the aircraft mission planned in 1997-1999. Cooperation with LAPAN on ground based measurements during aircraft observations was discussed. Also we invited a scientist from National Institute of Water and Atmosphere (NIWA) of New Zealand to discuss aerosol measurements inn technical detail.