SESAME Campaign (1994 - 1995)
The Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) was the second major European field campaign, to study the problem of the ozone layer destruction.
After evaluating the results of the first European campaign on the ozone problem (EASOE from January 1991 to March 1992) was evident that there were several gaps on the information obtained specially on the connection between polar ozone loss and its export to mid-latitude, as well as on the pre-winter development of the polar vortex, NOx reduction
and chlorine activation.
In 1993, was decided to perform a new campaign, with an extension of 2 years between January 1994 and April 1995 taking advantage of the experience gained during EASOE and the new or improved instrumentation developed afterwards. The majority of the scientists involved in SESAME were from Europe, but also from many other countries. In all, over 300 scientists from 21 countries took part.
The SESAME strategy was based on measurements at different times throughout the year of processes occurring in, and connecting, the lower stratosphere of high and middle northern latitudes. This required high quality measurements of ozone, active chemical species and stable species which were useful for tracing stratospheric transport processes, in conjunction with detailed meteorological studies. Three intensive periods were investigated: January-March 1994, September-October 1994 and December-April 1995. The first and last were periods when ozone loss was expected to occur, while the middle phase served to monitor conditions prior to the winter.
Compared to EASOE, the ground-based network for SESAME was extended in latitude and longitude, thanks to the collaboration with the Central Aerological Observatory of Moscow. Several research planes were part of the effort making flights in the Arctic, and large latitudinal surveys from autumn to spring, also a a Concorde Zebra shape flight off the coast of Norway was performed for studying the evolution of its contrail in the cold vortex. The timing of the ozonesonde ascents at all stations was organised so that they could probe the same air mass along an isentropic trajectory.
Stratospheric balloons were a fundamental part of the effort and as occured in EASOE, the main launch base was ESRANGE, near the Swedish city of Kiruna. Many of the flights for SESAME were flown over long distances and many were recovered in the Soviet Union which agreed to permit the overflights. Complementarily, a number of balloon flights were also performed from the Andoya Rocket Range in Norway, as well as the balloon bases of Aire-sur-l'Adour and Gap-Tallard in France. The 43 balloon flights were carried out under supervision of the balloon division of the French space agency CNES.
The campaign was scientifically very productive and (as ocurred with EASOE before) a good model for the way in which European resources, from both the European Commission and the individual countries, can be used to maximise the scientific return. By chance, the second SESAME winter of 1994/95 was the coldest in the 29 year record in the low stratosphere; ozone loss was large and easily detected by a variety of the SESAME measurements.
List of balloons launched during SESAME (incomplete)