The Atmospheric Chemistry and Transport of Ozone (ACTO) in the UTLS was a round 2 UTLS (Upper Troposphere and Lower Stratosphere) project led by Stuart Penkett, University of East Anglia.

This dataset collection contains airborne atmospheric chemistry data collected by the Met Research Flight (MRF) C-130 Hercules aircraft and atmospheric chemistry output.

Data were already collected on the composition and structure of the troposphere as part of OCTA, ACSOE, and TACIA programmes, UTLS-DCFZ and EU-MAXOX during campaigns in the first half of 1999. There was an obvious progression from the objectives of the previous experiments and those of this project. Therefore analysis of the data from these programmes were valuable for the planning of the new measurement campaign, which were collected in the UTLS using the UKMO C-130 during 40 hours flying time, in the spring/summer period of the 2000. Flights were 3-6 hours and did take place in the North Atlantic off northern Britain and were predominantly in the upper troposphere (4 to 11km) with only occasional sorties into the lower stratosphere. Flights were designed to examine the chemical composition and reactivity of different air masses: boundary layer air (marine and (polluted) continental); tropical and subtropical air; upper tropospheric and lower stratospheric air; and polar air. Detailed meteorological and chemical forecast data were obtained from ECMWF, UKMO and NILU. Domain filling trajectory calculations, with forecast wind fields, were used to locate layers and to determine their orientation, whilst the NILU chemical forecast model provided information on the expected chemical composition of the different air masses. To determine the origin, composition and chemical activity of the different air masses found in the UTLS, measurements were made from a large number of tracers, ozone precursors, reactive species and photochemical products.