Institute for Atmospheric ScienceSCHOOL OF EARTH AND ENVIRONMENT

Comparison of Measurements from the SCOUT-O3 Darwin and AMMA Campaigns with a 3-D Chemical

Transport Model

Wuhu Feng and Martyn Chipperfield

ACTIVE/SCOUT-O3/TWP-ICE/AMMA meeting, 9-11 January, Manchester

Acknowledgments: SCOUT-O3, H.Boenisch, C. Hoyle, B.M. Sinnhuber

OUTLINE

• Brief dscription of SLIMCAT/TOMCAT 3D CTM• Tracer Transport Experiment

- SCOUT WP 6.2• ‘Full chemistry’ TOMCAT runs

- SCOUT-O3- AMMA

• Conclusions

SLIMCAT/TOMCAT 3D CTM

Off-line chemical transport model with many different options.

Key points here:

• Extends to surface using hybrid - (SLIMCAT), -p (TOMCAT).

• Variable horizontal/vertical resolution.

• Horizontal winds and temperatures from (ECMWF) analyses.

• Vertical motion from diagnosed heating rates (SLIMCAT) or divergence (TOMCAT).

• Tropospheric physics: Tiedtke convection,

PBL: 2 Schemes: Louis / Holtslag and Boville

• Option of detailed tropospheric chemistry:

http://www.see.leeds.ac.uk/slimcat

• Louis (1979): (simple but still used in CTMs)

• PBL scheme (Holtslag and Boville, 1993)

Here C: concentration, Kc: eddy diffusivity, z: Height, reflects the nonlocal transport due to large eddy motion in the convective ABL. First term implies that scalar flux is always downgradient, the second term models the scalar flux as proportional to the strength of chemical flux of C from the surface

More information in Wang et al. (1999)

Boundary Layer Schemes in TOMCAT

z

CKcCw

''

)('' cz

CKcCw

SCOUT WP6.2: Idealised Tracer Experiments

SCOUT WP 6.2 is examining how well various CTMs capture transport to and within the TTL. The SCOUT CTMs are running idealised tracers, such as surface-emitted species with fixed lifetimes, to allow a direct comparison between the models.

More information: Chris Hoyle’s talk on Tuesday.

Tracers include:

• Tracers T5 (with 5 day lifetime) and T20 (20 day lifetime).• Idealised CO (prescribed OH loss and fixed surface mixing ratio).

WP6.2 Idealised CO Tracer

MLS CO (Schoeberl et al 2006)

SLIMCAT captures stratospheric CO tape recorder signal better than TOMCAT TOMCAT tropospheric uplift of CO extends too high (70-80 hPa)?

WP6.2 CO Tracer v Darwin Profile

Range of different TOMCAT/SLIMCAT runs with same surface boundary mixing ratio:

Different vertical coordinate, vertical diffusion, advection and resolution in CTM affect tracer transport.

16 Nov 2005

CO (ppbv) 1500

Obs‘TOMCAT’ (p-coord) CO too high in upper troposphere

SF6/CO2 simulations during SPURT Project

Simulation period 2000-2003 during SPURT campaign CTMs: TM5, TOMCAT and SLIMCAT 3 Tracers : SF6, CO2 and T500 (0→1). T500 is a prognostic tracer representing amount of air from the strat. “overworld”(0<500hpa,1>θ=380K)

Model details: TM5: 3°x2º, 45 vertical layers (ECMWF res. in UT/LS) TOMCAT/SLIMCAT: 5.6ºx5.6°, 24 vertical layers (1.5-2 km LS)

Comparisons in Bönisch et al., submitted, JGR.

SF6/CO2 simulations versus 4 SPURT Flights

Too weakStrat

Too weakTropo

V.Good

Comparison of SF6/CO2 as a function of distance to the local tropopause

Binned θ=5KTropopause=2PVU

θ= θ - θ TP

Seasonal lagin LMS

Large deviationmodel/measurement

Scatter due to strongconvection

CO2 Seasonal Cycle

(-----) Averaged surface constraints (35-65°N), (*) (x) trop to strat.

O3O3 H2O

H2O

HNO3

T

T

HNO3

Full Chemistry: SLIMCAT Comparison with MARSCHALS

TOMCAT Full Chemistry: Comparison with M55 Data: Darwin

H2O

O3

CLW

CO

T

LatAlt

Nov. 25, 2005 Nov. 30, 2005

FOZAN

FISH FLASH

TDL TOMCAT PBL

TOMCAT PBLTOMCAT PBL FOZAN

TOMCAT Full Chemistry Comparison with M55 Data: AMMA

O3

H2O

CO

T

LatAlt

August 7, 2006 August 13, 2006

FISH FLASH TOMCAT (ECMWF) TOMCAT (ECMWF)FISH

FOZAN TOMCAT: PBL Louis FOZAN

COCOT T

H2O

O3O3H2O

Comparison with M55 Data: AMMA

Large different CO different in TOMCAT between PBL/Louis schemes

August 7, 2006 August 13, 2006

PBL influence on the distribution of chemical speciesCO:PBL

CO:Louis

CO:Difference

Acetone:PBL

Acetone:Louis

Acetone:Difference

PBL influence on the distribution of chemical species

Conclusions

• SLIMCAT () has more realistic diagnosed stratospheric CO tape recorder than TOMCAT (p) confirming it gives better representation of stratospheric tracer transport than TOMCAT.

• Different vertical coordinate, vertical diffusion, advection and resolution in same CTM all affect tracer transport process (to different extents). (Bear in mind for model-model comparisons).

• Basic TOMCAT tropospheric model overestimates vertical transport to top of TTL (CO profiles).

Extra Slides

First different PBL schemes comparison in TOMCAT

Wang et al. (1999)

Randon profiles comparison at different locations which shows PBL scheme gives more realisticvertical distribution in the Troposphere than using Louisscheme

WP6.2 Tracer Transport Experiment

Different vertical coordinate, vertical diffusion, advection and resolution in CTM will affect tracer transport process

16 NOV 2005

Idealized 20 years run with two perpetual years 2000/2001 SLIMCAT and TOMCAT forced by different meteorology Different vertical diffusion schemes

WP6.1 Age of air experiment

SLIMCAT+OP has more realistic age of air, TOMCAT+ERA40 has the largest discrepancy

WP6.1 Age of air experiment: Mid-latitude

Different model configurations also affect the tracer transport in the mid-Latitude