As the polar spring arrives, the combination of returning sunlight and the presence of polar stratospheric clouds leads to splitting of chlorine compounds into highly ozone-reactive radicals that break ozone down into individual oxygen molecules. A single molecule of chlorine has the potential to break down thousands of molecules of ozone.
The ozone hole, first recognised in 1985, typically persists until November or December, when the winds surrounding the South Pole (polar vortex) weaken, and ozone-poor air inside the vortex is mixed with ozone-rich air outside it.
Envisat, the largest Earth observation satellite ever built, can localise ozone depletion and track its changes, enabling the rapid estimation of UV radiation as well as providing forecasting. The three atmospheric instruments aboard Envisat are the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), the global ozone monitoring by occultation of stars (GOMOS) sensor and the Michelson interferometer for passive atmospheric sounding (MIPAS).
In the framework of GMES (Global Monitoring of the Environment and Security), ESA has backed a project named TEMIS (Tropospheric Emission Monitoring Internet Service) that provides operational ozone and UV radiation monitoring based on SCIAMACHY and GOME-1 data. The ozone-monitoring data provided by these instruments span a time period of 11 years, which will be extended by the upcoming MetOp satellite series.
The first MetOp satellite in the series of three is scheduled to be launched in 2006 and will assist climate researchers in monitoring ozone levels and other atmospheric parameters. MetOp Europe's first polar-orbiting satellite and a mission dedicated to operational meteorology will include a next-generation ozone-monitoring instrument called GOME-2, intended to guarantee continuity of observation of this
Contact: Mariangela D'Acunto
European Space Agency