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  Information - AS3.07 Upper troposphere and lower stratosphere: dynamics and chemistry

Event Information
I suggest that this sesssion offers a better balance between dynamics and chemistry that would reflects the state of our understanding of the UTLS. In particular a subsession devoted to the tropical tropopause layer, the dehydration problem and chemistry in that region, would be very useful. Possible links exist with sessions on tropical convection and cirrus clouds.
If not possible, I would suggest a dedicated session on the tropical tropopause layer. Suggested conveners: J.P. Pommereau and T. Peter

Preliminary List of Solicited Speakers
SCOUT-O3 Research in the UTLS

Neil R.P. Harris and John A. Pyle
European Ozone Research Coordinating Unit
Centre for Atmospheric Science
University of Cambridge

Reliable prediction of the future evolution of the ozone layer and surface UV is required as a basis for informed decisions by policy makers. The state of the ozone layer over the next decades will depend on the interplay between climate change and the impact and evolution of ozone depleting substances such as CFCs. The Montreal Protocol has successfully reduced emissions and atmospheric concentrations of CFCs, which should return to their pre-ozone hole concentrations by about 2050. However, the ozone layer will most likely not return to its pre-ozone hole state, and so the central question of the Montreal process – how and when will ozone and UV radiation recover as CFC concentrations fall? – remains.
Research in SCOUT-O3, a major EU Integrated Project, is focusing on strengthening the European predictive capability through improving the use of coupled chemistry/climate models (CCMs). An improved understanding of model performance is gained from on-going validation and comparisons from existing and new measurements. Interpretation of the measurements is achieved using a variety of models operating on all spatial scales.
An improved understanding of processes in the upper troposphere and lower stratosphere in all regions of the world would significantly improve our predictive capability. Lack of knowledge about the tropical stratosphere and upper troposphere is being addressed in SCOUT-O3 through tropical field campaigns involving aircraft and balloons which will be used to investigate the detailed mechanisms by which air passes from the troposphere to the stratosphere. New fundamental information about chemical and microphysical processes gained from laboratory studies will improve the models used to interpret these measurements. Understanding of the larger scale importance is gained through analysis of satellite measurements (e.g. from ENVISAT and CALIPSO), meteorological analyses and other global fields.
Denitrification in the polar vortices is being studied to remove one of the major uncertainties regarding polar ozone loss. Better understanding of processes in the UTLS through modeling and data analysis and studies of the long-term variability in extratropical large scale transport are also being performed to improve long-term predictions of mid- and high latitude ozone and UV. Past and present variability in UV radiation is determined using re-evaluated and quality controlled data sets. Focussed studies involving measurements and modeling are used to improve understanding of how clouds and aerosols modify atmospheric radiation.
In this talk we will give an overview of the plans and early results from the SCOUT-O3 project, which O3 runs from May 2004 to April 2009 and is supported by the EC DG Research and national agencies.

TROCCINOX - Tropical Convection, Cirrus and Nitrogen Oxides Experiment, Overview

Ulrich Schumann (TROCCINOX Coordinator)

DLR Institut für Physik der Atmosphäre, Oberpfaffenhofen; 82230 Wessling (ulrich.schumann @

The EU project TROCCINOX (Tropical Convection, Cirrus, and Nitrogen Oxides Experiment), is being performed in 2002-2005 in cooperation with the Brazilian project TROCCIBRAS and in coordination with the EU-project HIBISCUS, within a large team of scientists, The project investigates the contributions of tropical continental deep convection to lightning-produced nitrogen oxides (NOx) and to other trace gases (including water vapour) and particles (ice crystals and aerosols). A first field campaign has been performed with the DLR Falcon aircraft during February and March 2004. A second field experiment is now being performed in Brazil between end of January and end of February 2005 including measurements with the Falcon and the high-flying M55 Geophysica aircraft. An overview of the measurements performed and the results obtained so far will be given. Among others, the data obtained so far are used to narrow uncertainties in present knowledge on the nitrogen oxides budget. Moreover the measurements are used to assess the accuracy of numerical weather prediction data of water vapour fields in the UTLS region.

HIBISCUS – Impact of tropical convection on the UTLS, Overview

Jean-Pierre POMMEREAU (HIBISCUS Coordinator)

CNRS Service d’Aéronomie, Verrières le Buisson 91371 France (

The EU project HIBISCUS is to study transport, microphysics and chemistry in the TTL (Tropical Tropopause Region) associated with deep tropical convection. The project makes use of short duration balloons flown close or within large convective cells in Brazil for high resolution tracers, water vapor, clouds and chemicals measurements, as well as circum-navigating long duration balloons – constant level superpressure and IR Montgolfier - and satellites for studying the impact of convective areas on the zonal distribution of the same parameters. The field campaign took place in January-March 2004 at 22°S in Brazil in cooperation with the Brazilian project TROCCIBRAS and in coordination with the EU-project TROCCINOX
An overview of the results will be given in introduction to several specific presentations planned in the session.


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