Centro di Eccellenza di Telerilevamento E Modellistica numerica per la Previsione di eventi Severi - Università degli studi dell'Aquila
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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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Seminario del 18 marzo 2015

Impact of climate change on stratospheric dynamics and chemical feedbacks

Prof. Martin Dameris
DLR-Institute of Atmospheric Physics
Oberpfaffenhofen, Germany

Mercoledì 18 marzo 2015 - h. 15:00-16:00
Aula 0.4 - Edificio Coppito blocco 0, Via Vetoio, L’Aquil

Abstract: Understanding of changes of stratospheric dynamics is necessary because they have a strong impact on climate and weather. Therefore analyses of global observations are needed in connection with numerical modelling, for investigations of dynamic processes relevant for explaining changes in chemistry and climate. For instance, the characteristics of the wind system in the upper troposphere and stratosphere (UTS) are important to be known for finding out the dynamical coupling / exchange of air between the stratosphere and troposphere and especially determining stratospheric ozone and water vapour concentrations. Currently largest uncertainties are existed in the tropics. Examples will be presented for ozone and water vapour based on results of the recent WMO ozone assessment, actual literature and my own research at DLR. There is an urgent need for investigations of dynamic and chemical processes by synergistic use of observations and data from numerical modelling to provide a better understanding of single processes and their feedbacks for climate change. In particular we have to investigate the changes of dynamics in future climate conditions, its impact on the ozone layer and its regional differences, and stratospheric water vapour fluctuations and its impact on the strength of climate change signals.
Biography: Prof. Martin Dameris is with DLR‐Institute of Atmospheric Physics, Oberpfaffenhofen, Germany. He studied Geophysics in Cologne (Germany), Diploma and PhD, Post‐Doc at Cologne University (Middle Atmosphere research). Since 1991: Research Scientist at DLR, since 1996: Lecturer and Prof. for Meteorology at the University of Munich (LMU), Coordinator of several international and national programs and projects, Member of international and national committees, Since 2001: Editor of the Journal Atmospheric Chemistry and Physics (ACP), Lead Author of several assessment reports, e.g. WMO Scientific Assessment of Ozone Depletion (2006, 2010, 2014), Author and co‐author of more than 100 papers.

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