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Institute for Atmospheric Science SCHOOL OF EARTH AND ENVIRONMENT

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

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Institute for Atmospheric Science SCHOOL OF EARTH AND ENVIRONMENT

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  1. 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 Acknowledgments: SCOUT-O3, H.Boenisch, C. Hoyle, B.M. Sinnhuber ACTIVE/SCOUT-O3/TWP-ICE/AMMA meeting, 9-11 January, Manchester

  2. OUTLINE • Brief dscription of SLIMCAT/TOMCAT 3D CTM • Tracer Transport Experiment • - SCOUT WP 6.2 • ‘Full chemistry’ TOMCAT runs • SCOUT-O3 • AMMA • Conclusions

  3. 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

  4. Boundary Layer Schemes in TOMCAT • 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)

  5. 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).

  6. 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)?

  7. WP6.2 CO Tracer v Darwin Profile 16 Nov 2005 ‘TOMCAT’ (p-coord) CO too high in upper troposphere Obs 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. 0 150 CO (ppbv)

  8. 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.

  9. SF6/CO2 simulations versus 4 SPURT Flights V.Good Too weak Tropo  Too weak Strat 

  10. Comparison of SF6/CO2 as a function of distance to the local tropopause Binned θ=5K Tropopause=2PVU  θ= θ- θTP Seasonal lag in LMS Large deviation model/measurement Scatter due to strong convection

  11. CO2 Seasonal Cycle (-----) Averaged surface constraints (35-65°N), (*)  (x) trop to strat.

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

  13. TOMCAT Full Chemistry: Comparison with M55 Data: Darwin Nov. 25, 2005 Nov. 30, 2005 Lat Alt  T CO TDL TOMCAT PBL CLW H2O FISH FLASH FOZAN FOZAN TOMCAT PBL TOMCAT PBL O3

  14. TOMCAT Full Chemistry Comparison with M55 Data: AMMA August 13, 2006 August 7, 2006 Lat Alt  T CO H2O FISH TOMCAT (ECMWF) FISH FLASH TOMCAT (ECMWF) FOZAN TOMCAT: PBL Louis O3 FOZAN

  15. Comparison with M55 Data: AMMA August 7, 2006 August 13, 2006 CO CO T T H2O O3 O3 H2O Large different CO different in TOMCAT between PBL/Louis schemes

  16. PBL influence on the distribution of chemical species CO:PBL Acetone:PBL CO:Louis Acetone:Louis CO:Difference Acetone:Difference

  17. PBL influence on the distribution of chemical species

  18. 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).

  19. Extra Slides

  20. First different PBL schemes comparison in TOMCAT Randon profiles comparison at different locations which shows PBL scheme gives more realistic vertical distribution in the Troposphere than using Louis scheme Wang et al. (1999)

  21. WP6.2 Tracer Transport Experiment 16 NOV 2005 Different vertical coordinate, vertical diffusion, advection and resolution in CTM will affect tracer transport process

  22. WP6.1 Age of air experiment • Idealized 20 years run with two perpetual years 2000/2001 • SLIMCAT and TOMCAT forced by different meteorology • Different vertical diffusion schemes • SLIMCAT+OP has more realistic age of air, TOMCAT+ERA40 has the largest discrepancy

  23. WP6.1 Age of air experiment: Mid-latitude • Different model configurations also affect the tracer transport in the mid-Latitude

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