Clouds reveal Europe’s ozone future

Forget blue skies research, it is clouds that have focused minds at the University of Leicester where scientists are tackling the causes of ozone depletion.

Atmospheric scientists in the Department of Physics and Astronomy are spearheading the MAPSCORE project, a European Commission Environment project which investigates a major cause of ozone depletion – high altitude polar clouds which activate the chlorine originally from CFCs and lead eventually to severe ozone destruction.

Leicester researchers have discovered it is possible to map the global distribution of polar clouds from space, and to determine their composition.

For the first time, scientists can see maps of clouds around the globe, via the internet, as soon as the ESA ENVISAT satellite detects them. This knowledge has already been put to good use in examining clouds and ozone loss near Europe during the last winter. Now the Leicester scientists are observing the evolution of the Antarctic ozone hole which last year behaved in a unprecedented fashion and showed that there are still surprises in the ozone story.

University of Leicester scientist Dr John Remedios, who is coordinating the MAPSCORE project, said: “ENVISAT makes it possible for us to map Polar Stratospheric Clouds in ‘near real-time’ for the first time. We have unprecedented detail and can even define the types of cloud that are driving ozone loss. This information guides our atmospheric modelling of how these polar stratospheric clouds form and their influence. This is important because we need to be able to predict how much ozone will be depleted in future years and polar stratospheric clouds are a key part of the problem”.

Clouds form in the polar stratosphere at altitudes of 12-28 km during the cold winter months. Chlorine from CFCs can be released from the surface of the cloud particles, and incident sunlight in the spring stimulates the rapid destruction of ozone by the ‘active’ chlorine in the polar stratospheric clouds. However, the overall occurrence and extent of PSCs in polar winter needs to be quantified, and it is here that ENVISAT’s daily monitoring of the atmosphere is vital as part of a wider effort to tackle this problem.

Dr John Remedios said: “For this reason, we are participating very actively in the latest European Commission campaign, ‘Vintersol’, which rallies over 300 scientists from over 14 European countries to tackle the problem of measuring and understanding the causes of mid-latitude ozone depletion, and to predict future ozone levels.” In the first Arctic phase, the Vintersol study was co-ordinated with a large NASA campaign, SOLVE-2, which gives a measure of the large international scientific effort involved in this work.

Stratospheric ozone levels over Europe have been decreasing at a rate of 6% per decade each spring, allowing more ultra-violet radiation to reach the ground. Information gleaned from the MAPSCORE project concerning ozone depletion by PSCs will enable Vintersol campaign scientists to identify future trends in ozone levels, and determine whether we can expect an increased health risk for Europeans of the future.

The MAPSCORE project is funded by the Environment Programme of the European Commission under Framework V. The Natural Environment Research Council has recently announced a new grant to support the development of the ENVISAT cloud mapping and to help Leicester scientists design a new space instrument which could perform an even better job of monitoring these important clouds.

The ENVISAT satellite is a major ESA mission monitoring the health of the planet.