Stratospheric chemistry and SMVGEAR II in GEOS-CHEM model

Gabriele Curci

University of L’Aquila

6/2/2003

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University

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

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University

STRATOSPHERIC CHEMISTRY �IN CURRENT GEOS-CHEM

6/2/2003

Gabriele Curci

Global sources and sinks of ozone (Tg O₃ y^-1) in GEOS-CHEM model

NO_x emissions (Tg N y^-1) to the troposphere

FOSSIL FUEL

23.1

​

AIRCRAFT

0.5

BIOFUEL

2.2

SOILS

5.1

LIGHTNING

5.8

STRATOSPHERE

0.2

BIOMASS

BURNING

5.2

GEOS-CHEM users’ meeting

Harvard University

STRATOSPHERIC CHEMISTRY �IN CURRENT GEOS-CHEM

• In UPBDFLX_MOD stratospheric O₃ (Synoz) and NO_x 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 NO_x are taken from Dylan Jones’ 2-D model

​

It would be helpful a better simulation of stratospheric chemistry?

6/2/2003

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University

A STRATOSPHERIC CHEMISTRY VERSION OF GEOS-CHEM

• 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

Gabriele Curci

MAIN FEATURES OF THE MODEL

GEOS-CHEM users’ meeting

Harvard University

A STRATOSPHERIC CHEMISTRY VERSION OF GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Stratospheric GEOS-CHEM ozone column

vs

TOMS column

(1998)

GEOS-CHEM users’ meeting

Harvard University

A STRATOSPHERIC CHEMISTRY VERSION OF GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Simulation of the Antarctic Ozone Hole

(1998)

GEOS-CHEM users’ meeting

Harvard University

SMVGEAR II IN GEOS-CHEM

• 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

6/2/2003

Gabriele Curci

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

MAIN FEATURES OF THE PACKAGE

GEOS-CHEM users’ meeting

Harvard University

SMVGEAR II IN GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Relative differences between SMV1 and SMV2 simulations after 1 month

NO_x

-1.6 ÷ 0.2 %

GEOS-CHEM users’ meeting

Harvard University

SMVGEAR II IN GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Relative differences between SMV1 and SMV2 simulations after 1 month

O_x

0 ÷ 1.6 %

GEOS-CHEM users’ meeting

Harvard University

SMVGEAR II IN GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Relative differences between SMV1 and SMV2 simulations after 1 month

CO

-0.55 ÷ 0 %

GEOS-CHEM users’ meeting

Harvard University

SMVGEAR II IN GEOS-CHEM: EVALUATION

6/2/2003

Gabriele Curci

Relative differences between SMV1 and SMV2 simulations after 1 month

OH

0 ÷ 10 %

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION

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

6/2/2003

Gabriele Curci

BASIC IDEA OF THE SIMULATION

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION

• It is implemented on:
• Version 5.02 (fvDAS compatibility, pressure fixer)
• GEOS-3 met-fields with 48 σ-levels
• NO_x-O_x-Hydrocarbons simulation (NSCRX=3)
• Uses SMVGEAR II chemistry solver
• 6 new tracers for the stratosphere: ClO_x, BrO_x, HCl, HBr, ClONO₂, BrONO₂ (total of 30 tracers)
• Revised O_x = 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

Gabriele Curci

MAIN FEATURES OF THE MODEL

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION

• Implementation of SMVGEAR II package
• Added C-preprocessor switch STRATCHEM to activate specific capabilities
• Enhanced labeling of trop/strat boxes
• Contemporaneous use of FAST-J and SLOW-J
• Implementation of stratospheric heterogeneous chemistry and PSCs sedimentation
• Revised O_x partitioning before call to chemistry solver

6/2/2003

Gabriele Curci

MAIN MODIFICATIONS TO THE CODE

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION: EVALUATION

6/2/2003

Gabriele Curci

Relative differences between STD and T-S simulations

O_x

0 ÷ 60 %

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION: EVALUATION

6/2/2003

Gabriele Curci

Zonal mean of O_x in January

GEOS-CHEM users’ meeting

Harvard University

TROPOSPHERIC-STRATOSPHERIC CHEMISTRY SIMULATION: EVALUATION

6/2/2003

Gabriele Curci

Zonal mean of O_x in January

GEOS-CHEM users’ meeting

Harvard University

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

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University

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

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University

END��☺ THANKS FOR YOUR ATTENTION! ☺

6/2/2003

Gabriele Curci

GEOS-CHEM users’ meeting

Harvard University