Institute for Atmospheric Science SCHOOL 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:

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

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

SF 6 /CO 2 simulations during SPURT Project  Simulation period during SPURT campaign  CTMs: TM5, TOMCAT and SLIMCAT  3 Tracers : SF 6, CO 2 and T500 (0→1). T500 is a prognostic tracer representing amount of air from the strat. “overworld”(0 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.

SF 6 /CO 2 simulations versus 4 SPURT Flights Too weak Strat  Too weak Tropo  V.Good

Comparison of SF 6 /CO 2 as a function of distance to the local tropopause Binned  θ=5K Tropopause=2PVU  θ= θ - θ TP Seasonal lag in LMS Large deviation model/measurement Scatter due to strong convection

CO 2 Seasonal Cycle (-----) Averaged surface constraints (35-65°N), (*)  (x) trop to strat.

O3 H2O HNO3 T T Full Chemistry: SLIMCAT Comparison with MARSCHALS

TOMCAT Full Chemistry: Comparison with M55 Data: Darwin H2OH2O O3O3 CLW CO TT Lat Alt Nov. 25, 2005Nov. 30, 2005 FOZAN FISHFLASH TDLTOMCAT PBL FOZAN

TOMCAT Full Chemistry Comparison with M55 Data: AMMA O3O3 H2OH2O CO TT Lat Alt August 7, 2006 August 13, 2006 FISHFLASHTOMCAT (ECMWF) FISH FOZANTOMCAT: PBL LouisFOZAN

CO TT H2OH2O O3 O3O3 H2OH2O Comparison with M55 Data: AMMA Large different CO different in TOMCAT between PBL/Louis schemes August 7, 2006August 13, 2006

PBL influence on the distribution of chemical species CO: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 realistic vertical distribution in the Troposphere than using Louis scheme

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