OTHER OF

IGAC

MODELLING OF CHANGES

IN STRATOSPHERIC OZONE AND OTHER TRACE GASES DUE TO EMISSION CHANGES

(EEC STEP-PROJECT)

Project leader: Ivar S. A. ISAKSEN

Co-worker: Frode STORDAL, University of Oslo, Dept. of Geophysics, P.O. Box 1022 Blindern, 0315 Oslo 3, Norway

Co-worker: Claire CRANIER, Service d'Aeronomie CNRS, P.B. 3, 91371 Verrieres Ie Buisson Cedex, France ·

Co-worker: Guido VISCONTI, Universita degli Studi J'Aquila, Dipartimento di Fisica, Piazza Annunziata I, l'Aquila, Italy

Co-worker : Niels LARSEN, Danmarks Meteorologsike lnstitut, Lyngbyvej 100, Copenhagen, Denmark

Co-worker: Dominique FONTEYN, Belgisch lnstituut voor Ruimte-Aeronomie, Ringlaan 3, B-1180 Brussel, Belgium

This research aims at modelling of stratospheric ozone and other trace gases (hydrogen family, nitrogen family, chlorine family and carbon family and others) using the BISA-2D-model.

Description of two dimensional BISA-model of the middle atmosphere The model, developped at the institute, is a two dimensional model (altitude, latitude) of the zonal mean middle atmosphere extending from 0 km up to 55 km. The dynamics, the chemistry and the radiation of the middle atmosphere are coupled, thus allowing for important interactions (e.g. chemically altered ozone will change the dynamics through the modified radiation).

Due to the formulation in a isentropic framework, a consistent dynamics is obtained in the model, which contains a full chemistry and radiation package.

The chemistry package includes the current state of the art homogenous phase

chemistry and heterogenous chemistry in an experimental stage. This allows

the model to be used for hindcasting using an observed temperature distribution

of the middle atmosphere as the only dynamical input. The resulting model

calculations can be compared with observations to improve the knowledge

of the chemistry of the middle atmosphere (such as the ozone hole; dynamics

versus chemistry). The model can also be used for forecasting or prediction

studies; in this case a predicted temperature from a climatological model will

be used as input in the model consistently with the emission changes of trace

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Figure 1.

The ozone distribution (expressed in parts per million by volume) for January with present day co nditions.

gases (e.g. CO

CFC's, CH

etc.). The model then predicts changes in chemically active trace gases. Figure 1 shows the calculated ozone distribution for January with present day conditions.

Research topics

The main research topic is the influence of emission changes on stra- tospheric ozone. This covers a wide variety of problems.

1. Due to the evolution of the scientific understanding of the middle atmosphere, the BISA-2D-model is continually updated.

2. It is now well understood that the increase in CFC's in the atmosphere causes an increase in active chlorine amount in the stratosphere. This active chlorine destroys ozone through a catalytic cycle. Different scenario's, with or without CFC-replacements, are used to study the influence on ozone depletion.

3. The vulcanic eruptions, like Pinatubo (1991), change the statospheric ozone behaviour; research is performed on these processes.

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4. Aircraft industry is preparing projects for a massive stratospheric supersonic fleet for civil use. The emission products of these aircraft engines have the potential to change the stratospheric ozone, specially in the northern hemisphere. Since these emissions are locally, the dynamics plays an important role and studies are underway to establish the influence of the dynamics on the ozone changes.

5. Since in the stratosphere, the dynamics, the chemistry and the radiation are susceptible to temperature changes, studies are planned to couple this model with a climate model to investigate on the influence of the greenhouse effect.

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