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Notizie Flash

THE OZONE HOLE STORY: A MODEL FOR ADDRESSING CLIMATE CHANGE

Prof. William H. Brune
Pennsylvania State University (USA)

Mercoledì 16 aprile 2015 - h. 14:30
Aula 1.6
- 1° piano, Coppito I, Via Vetoio, L’Aquila

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Seminario del 16 aprile 2015

THE OZONE HOLE STORY: A MODEL FOR ADDRESSING CLIMATE CHANGE

Prof. William H. Brune
Pennsylvania State University (USA)

Mercoledì 16 aprile 2015 - h. 14:30
Aula 1.6
- 1° piano, Coppito I, Via Vetoio, L’Aquila

Abstract: At a time when there is still debate among the public and politicians about the link between climate change and the greenhouse gases expelled into the atmosphere by the activities of human beings, in this seminar we look back to an argument from another era. In many ways, today’s controversy over the causes of climate change and what to do about it are reminiscent of the debate over the link between chlorofluorocarbons (CFCs) and the thinning of the ozone layer over 30 years ago, when the vast majority of scientists were on one side, and industry and lobbyists were on the other. This stalemate was finally resolved only after the discovery of the ozone hole over Antarctica and the irrefutable evidence linking the ozone hole to CFCs. Only then did the major manufacturers of CFCs begin to get on board. In the end, an international agreement was signed to control CFC production, substitutes for the compounds were found and marketed by manufacturers, and the ozone hole stopped growing and it now shows signs of repairing itself, if slowly. This collaboration has been hailed as a landmark. But was that the whole story?

Biography: William H. Brune is a distinguished professor at Pennsylvania State University, USA. In 1978, Brune received a Ph.D. in physics from Johns Hopkins University for his research on ultraviolet observations of comets, hot stars, and the diffuse galactic background. For the next ten years, he was a Research Associate at Harvard University, where he studied the chemistry that causes stratospheric ozone loss, developing unique aircraft instruments to observe reactive halogens in the Antarctic vortex. He joined the faculty of the Pennsylvania State University in 1988, where he was the Head of the Department of Meteorology for the past 15 years. Since 1988, he has been studying the fast chemistry in the lower atmosphere, introducing state-of-the-art instruments for aircraft observations of the atmosphere’s primary reactive gases and, recently, he proposed the concept of potential aerosol mass, which can be defined as the maximum aerosol mass that the oxidation of precursor gases produces.

 
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Seminario 19 marzo 2015

Impact of the early winter sea ice anomaly on the stratospheric circulation

P. Ruggieri
DSFC – CETEMPS, Università dell’Aquila

Giovedì 19 marzo 2015
h. 15:00, Sala Riunioni 1° piano
Dipartimento di Scienze Fisiche e Chimiche, Coppito, L’Aquila


Abstract: In the early years of the new century many studies proved that the stratospheric anomalies which can perturb the tropospheric state are generated by the troposphere itself. It became clear, year after year, that the interaction between the troposphere and the stratosphere on intraseasonal time scales is actually a two way coupling rather than a one-way forcing. Thus, it seemed reasonable that the earth surface is one of the primary sources of stratospheric changes and phenomena as sudden stratospheric warmings can be caused by the propagation of planetary waves triggered in the lower troposphere.
According to Rossby waves theory, when those waves break through the tropopause, they are likely to be reflected backward or absorbed when they reach the edge of the stratospheric polar vortex, thus lowering its intensity. In turn, the increased waviness and a southward shift of the jet may favor the onset of a secondary vertical circulation, which generates a sinking motion in the polar cap, raising the pressure in the high latitude troposphere (i.e. leading to a negative phase of the Arctic Oscillation). Recent results suggest that sea ice loss in the Barents and Kara seas (B-K) in autumn and early winter can cause a weakening of the stratospheric polar vortex in the subsequent months. Hence the rapid decline of sea ice in B-K has stimulated great interest into the potential feedback between sea ice and tropospheric anomalies modulated by the variability of the stratospheric polar vortex.
The role of the stratosphere in the above mechanism is discussed and a quasi-geostrophic theory for the coupling is analysed. Results based on 16 years of reanalyses from the European Centre for Medium-Range Weather Forecasts are shown and compared with a forced simulation with a simplified Atmospheric General Circulation Model provided by the Abdus Salam International Centre for Theoretical Physics. The potential impact on the weather in the Euro-Atlantic sector is discussed thereafter.
Biography: Paolo Ruggieri is a PhD student at University of L’Aquila and recently graduated in physics with a thesis on ‘The impact of Barents-Kara sea ice variability on the Euro-Atlantic Sector”.
The seminar is based on’ Ruggieri P., R. Buizza, G. Visconti, European weather sensitivity to Barents-Kara sea-ice variability’ Geophysical Research Abstracts Vol. 17, EGU2015-2550-3, 2015 EGU General Assembly 2015’.

 
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