A multi-model analysis of the

tropospheric ozone budgetDavid Stevenson1, F.J. Dentener2, M.G. Schultz3, K. Ellingsen4, T.P.C. van Noije5, O. Wild6,

G. Zeng7, M. Amann8, C.S. Atherton9, N. Bell10, D.J. Bergmann9, I. Bey11, T. Butler12, J. Cofala8, W.J. Collins13, R.G. Derwent14, R.M. Doherty1, J. Drevet11, H.J. Eskes5,

A.M. Fiore15, M. Gauss4, D.A. Hauglustaine16, L.W. Horowitz15, I.S.A. Isaksen4, M.C. Krol2, J.-F. Lamarque17, M.G. Lawrence12, V. Montanaro18, J.-F. Müller19, G. Pitari18,

M.J. Prather20, J.A. Pyle7, S. Rast3, J.M. Rodriguez21, M.G. Sanderson13, N.H. Savage7, D.T. Shindell10, S.E. Strahan21, K. Sudo6, and S. Szopa16

1. University of Edinburgh, School of GeoSciences, Edinburgh, United Kingdom. 2. Joint Research Centre, Institute for Environment and Sustainability, Ispra, Italy. 3. Max Planck Institute for Meteorology, Hamburg, Germany. 4. University of Oslo, Department of Geosciences, Oslo, Norway.

5. Royal Netherlands Meteorological Institute (KNMI), Atmospheric Composition Research, De Bilt, the Netherlands. 6. Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan. 7. University of Cambridge, Centre of Atmospheric Science, United Kingdom.

8. IIASA, International Institute for Applied Systems Analysis, Laxenburg, Austria. 9. Lawrence Livermore National Laboratory, Atmos. Science Div., Livermore, USA. 10. NASA-Goddard Institute for Space Studies, New York, USA. 11. Ecole Polytechnique Fédéral de Lausanne (EPFL), Switzerland.

12. Max Planck Institute for Chemistry, Mainz, Germany. 13. Met Office, Exeter, United Kingdom. 14. rdscientific, Newbury, UK. 15. NOAA GFDL, Princeton, NJ, USA. 16. Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France.

17. National Center of Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO, USA. 18. Università L'Aquila, Dipartimento di Fisica, L'Aquila, Italy. 19. Belgian Institute for Space Aeronomy, Brussels, Belgium.

20. Department of Earth System Science, University of California, Irvine, USA 21. Goddard Earth Science & Technology Center (GEST), Maryland, Washington, DC, USA.

Tropospheric ozone budget• Ozone is an important greenhouse gas and air pollutant

• Ozone budget and lifetime crucial for:– Long-range transport– Global Warming Potentials– Oxidising capacity– Climate-Chemistry (radiative forcing and feedbacks)

• Previous intercomparisons (e.g. IPCC TAR literature survey) of modelled tropospheric ozone budget hampered by:– Definition of PO3 and LO3

– Definition of troposphere– Differences in emissions

• What we really want to understand are differences due to model formulation (chemistry, convection, resolution, mixing, boundary conditions…)

Defining the O3 or Ox budget

NO2 L: O3 + HO2

O3 + OHO(1D) + H2OO3 + alkenes

O3 deposition

O3O(3P) O(1D)

Stratospheric input

PAN

HNO3

HO2NO2

NO3

N2O5

dep

dep

NO

P: NO + RO2 + other net loss terms

Some studiesuse wider definition;should make only minor difference

Different model chemical schemes – potential source of differences

ACCENT Intercomparison

• Prescribed anthropogenic emissions– but modellers used their own natural emissions, so

still some emissions uncertainty

• Defined O3 budget terms– but some modellers used their own definitions,

specific to chemical scheme– requested 3D monthly mean P and L

– also O3 deposition; inferred stratospheric input

• Defined tropopause O3=150 ppbv– centralised analysis

20 Models supplied O3 budgets

• CHASER_CTM• CHASER_GCM• FRSGC/UCI• GEOS-CHEM• GMI/CCM3• GMI/DAO• GMI/GISS• LLNL-IMPACT• LMDz/INCA-CTM• LMDz/INCA-GCM

• MOZ2-GFDL• MOZART4• MOZECH• MOZECH2• STOCHEM-HadAM3• STOCHEM-HadGEM• TM4• TM5• ULAQ• UM_CAM

CTMs driven by analyses

CTMs driven by GCM outputCTMs coupled to GCMs

S1 Tropospheric O3 budget

-5000

50010001500200025003000350040004500500055006000650070007500

CH

AS

ER

_CT

M

CH

AS

ER

_GC

M

FR

SG

C

GE

OS

-CH

EM

GF

DL

GM

ICC

M

GM

IDA

O

gm

igis

LL

NL

-IM

PA

CT

LM

DzI

NC

A

LM

DzI

NC

Ac

MO

ZE

CH

NC

AR

ST

OC

HE

M_H

adA

M3

ST

OC

HE

M_H

adG

EM

TM

4

TM

5

UL

AQ

UM

_CA

M

Mea

n

Med

ian

Tg

O3/

yr

P L P-L D Sinf

Year 2000 Tropospheric O3 budget

Tg(O3)/yr P L D SinfB/Tg(O3) /days

ACCENT 5100 4670 1000 550 340 22IPCC TAR 3420 3470 770 770 300 24

Zonal Annual Mean Ozone chemical production

Relatively highvalues through

whole troposphere

Relatively lowvalues in

tropical UT

Differences at poles

Ozonechemical

productionmainly reflects

NOx distributions

Zonal Annual Mean Ozone chemical destruction

Ozonechemical

destructionmainly reflects

H2O distribution(also O3 distribution)

Zonal Annual Mean Ozone net chemical production

Surface level O3 Net Chemical Production

Multi-model ensemble mean ozone P, L, NCP

= 0.997 Surface

Ship NOx

Multi-model ensemble mean ozone P, L, NCP

= 0.975

Multi-model ensemble mean ozone P, L, NCP

= 0.930

Multi-model ensemble mean ozone P, L, NCP

= 0.870

Multi-model ensemble mean ozone P, L, NCP

= 0.792 Mid-tropnet destruction

Multi-model ensemble mean ozone P, L, NCP

= 0.700 Mid-tropnet destruction

Multi-model ensemble mean ozone P, L, NCP

= 0.600 Mid-tropnet destruction

Multi-model ensemble mean ozone P, L, NCP

= 0.505

Multi-model ensemble mean ozone P, L, NCP

= 0.422

Multi-model ensemble mean ozone P, L, NCP

= 0.355Upper-trop

net productionlightning

Multi-model ensemble mean ozone P, L, NCP

= 0.300Upper-trop

net productionlightning

Multi-model ensemble mean ozone P, L, NCP

= 0.250Upper-trop

net productionlightning

Multi-model ensemble mean ozone P, L, NCP

= 0.200Upper-trop

net productionlightning

Multi-model ensemble mean ozone P, L, NCP

= 0.150Upper-trop

net productionlightning

Multi-model ensemble mean ozone P, L, NCP

= 0.099Upper-trop

net productionlightning

Global O3 budget terms

O

3 lif

etim

e / d

ays

O3 burden / Tg(O3)

Results for asingle model,several scenarios

Colours signifydifferent models

Ensemble mean model (offset)

Higher burdengoes with

longer lifetime

Climate changeshortens lifetimebut burden canrise/fall

As emissions rise,burden increases,

lifetime falls

MFR

A2

Conclusions

• First well-constrained analysis of several model’s ozone budgets, with consistent definitions of budget terms, tropospheric domain, and anthropogenic emissions

• Broadly consistent gross features• Production reflects NOx distribution• Destruction reflects H2O (and O3) distribution• Some inter-model differences in lightning NOx/convection;

isoprene; H2O; polewards transport; BL• Quite large differences compared to IPCC TAR

– NOx and isoprene emissions– Stratospheric input

• Deposition also crucial; most of the O3 budget is in BL

Further information

• Dentener et al., in press, Env. Sci. Tech.– Overview of intercomparison

• Stevenson et al., in press, JGR– Tropospheric O3 and CH4

• Van Noije et al., in press, ACPD– NO2 columns, modelled & GOME

• Shindell et al., submitted, JGR– CO, modelled & MOPITT

• Dentener et al., submitted, GBC– Deposition of N and S

• Ellingsen et al., in prep.– Surface O3 air quality

• +probably more• dstevens@staffmail.ed.ac.uk