Report to the European Union on the work performed within GIM/IGAC activity on 3-D global simulations of tropospheric chemistry with focus on ozone distributions

Directorate-General For Research And Innovation European Commission

Description

Results on the GIM/IGAC intercomparison 1997 exercise
Environmental research
Environment policy and protection of the environment

Sujets

• Sciences et techniques

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• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 8
• Langue: English
• Poids de l'ouvrage: 9 Mo

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European Commission
Community Research
General information
3-D global simulations of
tropospheric chemistry with focus
on ozone distributions
results of the GIM/IGAC
intercomparison exercise
TGAC
ENERGY, ENVIRONMENT
AND SUSTAINABLE DEVELOPMENT
EUR 18842 EUROPEAN COMMISSION
Edith CRESSON, Member of the Commission
responsible for research, innovation, education, training and youth.
DG XII/D.2 — RTD actions: Climate and natural hazards
Contact: Mr. G. Angeletti
Address: European Commission, rue de la Loi/Westraat 200 (SDME 7/53),
B-1049 Brussels — Tel. [phone]; fax [phone];
e-mail: giovanni. angeletti@dg 12.cec.be European Commission
Report to the European Union on the work performed within GIM/IGAC activity on
3-D global simulations
of tropospheric chemistry
with focus on ozone distributions
Results of the
GIM/IGAC intercomparison 1997 exercise
M. Kanakidou(12), F. J. Dentener(3), G. P. Brasseur(4), W. J. Collins(5), T. K. Berntsen3),
D. A. Hauglustaine(47), S. Houweling(3), I. S. A. Isaksen(6), M. Krol(3), K. S. Law(4),
M. G. Lawrence(8), J. F. Muller(9), P. H. Plantevin(14), N. Poisson(113),
G. J. Roelofs(3), Y. Wang(10'11), W. M. F. Wauben(12)
(1) Laboratoire des sciences du climat et de I'environnement, Unite mixte CNRS/CEA,
Orme des Merisiers, CE Saclay, F-91191 Gif-sur-Yvette Cedex
(2)Now at University of Crete, Department of Chemistry, Environmental Chemical Processes Laboratory, PO Box 1470,
71409 Heraklion, Greece, [e-mail]
(3) Utrecht University, IMAU, Utrecht, The Netherlands
(4) Atmospheric Chemistry Division — NCAR, Boulder, Colorado, United States
(5)c Chemistry Modelling, Meteorological Office, Bracknell, United Kingdom
(6) University of Oslo, Oslo, Norway
7)Service d'Aeronomie, Universite Paris 6, Jussieu, Paris, France
(8) Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Germany
(9) Belgian Institute for Space Aeronomy, Brussels, Belgium
(10) Harvard University, Cambridge, Massachusetts, United States
(11)Now at Georgia Institute of Technology, Atlanta, United States
(12) KNMI, De Bilt, The Netherlands
(13) Now at 10
(14) Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, United Kingdom
December 1998
1999 EUR 18842 EN Published by the
EUROPEAN COMMISSION
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Cataloguing data can be found at the end of this publication.
Luxembourg: Office for Official Publications of the European Communities, 1999
ISBN 92-828-5928-2
© European Communities, 1999
Printed in Belgium IGAC/3-D CTM 03 intercomparison exercise
OBJECTIVES.
The objective of the Tropospheric Ozone (03) Global Model Intercomparison Exercise performed in
1997 was to systematically evaluate the capabilities of current generation of 3-dimensional global models to
simulate tropospheric ozone and their precursor gases, and to identify key areas of uncertainty in our
understanding of the tropospheric 03 budget. This exercise was organised by GIM (Global Integration
Modelling) Activity of the IGAC (International Global Atmospheric Chemistry) Project. Thirteen 3-
dimensional global chemistry/transport models participated at this exercise. Significant differences have been
detected between the models although all of them capture the general patterns in the global distribution of
carbon monoxide, nitrogen oxides and ozone. Since at the time of instigating this intercomparison, most of
the models were in the process of being developed, this exercise helped critically improving the model
parametrisations.
1. STATE OF ART.
It is now recognised that the atmospheric concentrations of several chemical and radiatively important trace
constituents (gases and particles) are changing in the atmosphere (IPCC, 1994). Human activity is the main
reason for these changes, climate changes affecting natural emissions and the radiative balance of the earth
being the second forcing agent. Indeed, several trace constituents like aerosols, methane (CH4), nitrous oxide
(N20), nitrogen oxides (NOx = NO + N02), carbon monoxide (CO), Non-Methane Volatile Organic
Compounds (NMVOC) including Non-Methane Hydrocarbons (NMHC), sulfur dioxide (S02),
dimethylsulfide (DMS) and halocarbons have direct anthropogenic and/or natural emissions to the
atmosphere. Others, like ozone (03) and secondary aerosols, are produced from chemical reactions initiated
by their precursors. In turn, the changing atmospheric concentrations of these trace constituents could affect
the radiative balance of the earth and may lead to a climate change.
To understand and reliably predict chemical and climate changes in the atmosphere a thorough
understanding of the chemical, physical, biological and climatic processes which affect the distributions of
trace compounds in the atmosphere, and of the interactions between these processes is required. The global
budgets of trace constituents, their evolution due to natural and anthropogenic forcing, and the related
feedback mechanisms can be simulated by the means of numerical models.
The use of numerical models is required to take into account the physical processes governing the budget of
trace gases in the troposphere and the complex non-linear behaviour of chemical reactions in the
troposphere. Such models integrate the most recent information on chemical kinetics of homogeneous and
heterogeneous reactions as well as photodissociation coefficients of atmospheric molecules. They also
account for interactions between transport, chemistry and the radiative budget in the troposphere, and
specifically for i) transport of trace constituents like nitrogen species (NOy) and 03 from the stratosphere,
ii) emissions of trace gases like 03 precursors such as N0X, CO, NMVOCs, and aerosols occurring mainly
in the low troposphere, iii) dry deposition of various trace gases and particles on the earth's surface, iv) wet
removal of soluble gases and particles, v) convection, vi) planetary boundary layer mixing, vii) cloud
microphysics and viii) homogeneous and heterogeneous chemical reactions.
Recent assessments of the global-scale, radiative effects of greenhouse gases and of aerosols have been
performed on the basis of global models which, in most cases, are still under development. The accuracy of
such calculations relies strongly on the capability of the models to simulate the global budget of trace gases
and aerosols. A major concern for the calculation of the chemically reactive trace gases budgets is associated IGAC/3-D CTM 03 intercomparison exercise
with 1. the inaccuracies in the transport parameterisation, 2. the simplification of the chemistry in the
troposphere, required due to the computationally prohibitive number of chemical reactions and species and
3. the uncertainties in the trace gases emissions used in the global models.
Current models often ignore certain important chemical and radiative processes in the atmosphere, making it
necessary to further improve models in order to attain better estimates of the budgets of 03 , CH4, CO and
N0X. Indeed, 03 is a greenhouse gas, a pollutant and one of the major oxidising agents in the troposphere.
CH4 is the most chemically important greenhouse gas with direct emissions to the atmosphere. N0X, which
is also a pollutant, controls 03 chemical production and destruction in the troposphere. CO is a chemically
important gas with primary and secondary emissions in the atmosphere. Depending on the ambient N0X
mixing ratios, CO oxidation by hydroxyl (OH) radicals forming hydrogen peroxy radicals (H02) enhances
(high N0X) or depletes (low N0X) ozone in the troposphere (Crutzen, 1994). CO changes have feedbacks
into the abundance of CH4 through the alteration of OH (Prather, 1996). Thus, although CO itself is not a
significant greenhouse gas, changes in its concentration affect ozone and CH4, both significant greenhouse
gases (Daniel and Solomon, 1998).
Assessment was started by WMO/IPCC in 1994 (Stordal et al., 1994, Olson et al., 1997) to evaluate the
capability of the chemical models to simulate O3, N0X, H0X and VOC chemistry. This effort was continued
by the GIM (Global Integration Modeling) Activity within the IGAC (International Global Atmospheric
Chemistry) Project of IGBP in 1996-1997, and focused on the capability of the global three-dimensional
chemistry transport models (CTMs) used for global chemical and climate simulations to calculate the O3
budget. Ground-based and in-situ observations from several regions of the globe are used for validation of
the model results. Although, the 1997 intercomparison exercise focused on the model capability to simulate
ozone, the calculated distributions of nitrogen oxides (NOx) and carbon monoxide (CO) have been also
compared to highlight the differences in ozone simulations. In addition, carbone has been compared
to observations at selected surface stations, since it is a key compound for tropospheric chemistry.
Moreover, car