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Stratospheric chemistry and SMVGEAR II in GEOS-CHEM model

This study explores the new enhancements in the GEOS-CHEM model, focusing on the full simulation of stratospheric chemistry using the SMVGEAR II solver. The evaluation of these new capabilities is discussed along with the implications for future developments and possible applications.

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Stratospheric chemistry and SMVGEAR II in GEOS-CHEM model

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  1. Stratospheric chemistry and SMVGEAR II in GEOS-CHEM model Gabriele Curci University of L’Aquila 6/2/2003

  2. ROAD MAP • Role of the stratosphere in GEOS-CHEM model • New capabilities of GEOS-CHEM: • Full Stratospheric chemistry simulation • SMVGEAR II chemistry ODE solver • Tropospheric-Stratospheric chemistry simulation • First evaluation of new capabilities • Conclusions and development needs • Possible applications 6/2/2003

  3. STRATOSPHERIC CHEMISTRY IN CURRENT GEOS-CHEM Global sources and sinks of ozone (Tg O3 y-1) in GEOS-CHEM model NOx emissions (Tg N y-1) to the troposphere STRATOSPHERE 0.2 LIGHTNING 5.8 FOSSIL FUEL 23.1 SOILS 5.1 BIOMASS BURNING 5.2 BIOFUEL 2.2 AIRCRAFT 0.5 6/2/2003

  4. STRATOSPHERIC CHEMISTRY IN CURRENT GEOS-CHEM • In UPBDFLX_MOD stratospheric O3 (Synoz) and NOx fluxes are specified • Reactions with OH and photolysis of tracers are performed in SCHEM after call to SMVGEAR • Monthly mean stratospheric OH, J-values, Prod/Loss of CO and NOx are taken from Dylan Jones’ 2-D model It would be helpful a better simulation of stratospheric chemistry? 6/2/2003

  5. A STRATOSPHERIC CHEMISTRY VERSION OF GEOS-CHEM MAIN FEATURES OF THE MODEL • It shares with standard model: • Input met fields • Transport module • SMVGEAR chemistry ODE solver • Stratospheric chemistry mechanism derived from STRATAQ model from U. of L’Aquila [Grassi et. al, 2002] • 40 species, 120 kinetic reactions, 30 photolysis, 6 heterogeneous reactions • Heterogeneous chemistry on sulfate aerosol and PSCs • PSC sedimentation (denitrification) • 17 transported tracers + 8 long-lived species w/ fixed distribution (CH4, N2O, CFCs, CH3Cl, CH3Br…) • Computes J-values using “SLOW-J” algorithm 6/2/2003

  6. A STRATOSPHERIC CHEMISTRY VERSION OF GEOS-CHEM: EVALUATION Stratospheric GEOS-CHEM ozone column vs TOMS column (1998) 6/2/2003

  7. SMVGEAR II IN GEOS-CHEM MAIN FEATURES OF THE PACKAGE • Sparse-Matrix-Vectorized Gear type chemical ODE solver version 2 • Main differences vs. SMVGEAR version 1: • Allows for different chemistry sets in different regions of the atmosphere (e.g., urban, free troposphere, stratosphere) • Grid reordering according to stiffness for computational efficiency • A GEOS-CHEM 1-month run using SMVGEAR II reveals: • 20 min/day vs. 23 min/day on IBM/AIX platform • 10 h/month vs. 11.5 h/month on IBM/AIX platform • different concentrations 6/2/2003

  8. SMVGEAR II IN GEOS-CHEM: EVALUATION Relative differences between SMV1 and SMV2 simulations after 1 month NOx -1.6 ÷ 0.2 % 6/2/2003

  9. SMVGEAR II IN GEOS-CHEM: EVALUATION Relative differences between SMV1 and SMV2 simulations after 1 month Ox 0 ÷ 1.6 % 6/2/2003

  10. SMVGEAR II IN GEOS-CHEM: EVALUATION Relative differences between SMV1 and SMV2 simulations after 1 month CO -0.55 ÷ 0 % 6/2/2003

  11. SMVGEAR II IN GEOS-CHEM: EVALUATION Relative differences between SMV1 and SMV2 simulations after 1 month OH 0 ÷ 10 % 6/2/2003

  12. IF ( LEVEL < TROPOPAUSE ) THEN STANDARD TROPOSPHERIC CHEMISTRY MECHANISM 80 species, 288 kinetic reactions, 51 photolysis, 5 heterogeneous reactions ELSE NEW STRATOSPHERIC CHEMISTRY MECHANISM 40 species, 120 kinetic reactions, 30 photolysis, 6 heterogeneous reactions TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION BASIC IDEA OF THE SIMULATION 6/2/2003

  13. TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION MAIN FEATURES OF THE MODEL • It is implemented on: • Version 5.02 (fvDAS compatibility, pressure fixer) • GEOS-3 met-fields with 48 s-levels • NOx-Ox-Hydrocarbons simulation (NSCRX=3) • Uses SMVGEAR II chemistry solver • 6 new tracers for the stratosphere: ClOx, BrOx, HCl, HBr, ClONO2, BrONO2 (total of 30 tracers) • Revised Ox = O3+NO2+2NO3+O+O(1D)to make it suitable for the stratosphere • Photorates: FAST-J in the troposphere and SLOW-J in the stratosphere 6/2/2003

  14. TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION: EVALUATION Relative differences between STD and T-S simulations Ox 0 ÷ 60 % 6/2/2003

  15. TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION: EVALUATION Zonal mean of Ox in January 6/2/2003

  16. CONCLUSIONS AND DEVELOPMENT NEEDS • New capabilities have been developed to improve stratospheric chemistry simulation into GEOS-CHEM model: • Full stratospheric chemistry model • Tropospheric-stratospheric chemistry model to be improved • The new simulations require deep changes to the code • Changes imply adaptation of other parts of the code (diagnostics, other simulation types…) • The new code is not yet implemented for parallel computing 6/2/2003

  17. POSSIBLE APPLICATIONS • STE and stratospheric influence studies • Comparison of GEOS and fvDAS data (cross-tropopause fluxes) • Satellite data retrieval (better a-priori for the stratosphere) • Halogen chemistry • Chemistry-radiation feedback (compute J-values using calculated O3) 6/2/2003

  18. END THANKS FOR YOUR ATTENTION!  6/2/2003

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