FIRST GEOS-CHEM USERS’ MEETING�June 2-3 2003

Why are we here?

• Exchange model information and experience
• Identify priorities for model development
• Establish protocols for code management and development, relationships between users

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The GEOS-CHEM user community

HERITAGE OF GEOS-CHEM MODEL

Harvard-GISS CTM

(Prather et al., 1987)

Tropospheric O₃ simulation

(Horowitz et al., 1998; Liang et al., 1998; Wang et al., 1998)

GEOS-CTM

(Allen et al., 1996)

GEOS-CHEM CTM

for tropospheric O₃

(Bey et al., 2001)

Sulfate simulation

(Chin et al., 1996)

GOCART aerosol model (Chin et al., 2000)

Current GEOS-CHEM CTM

fvGCM at GMAO

(data assimilation)

NASA GMI (assessment)

CO₂ simulation

(Suntharalingam

et al.. 2003)

EPA CMAQ

(regional air quality)

CACTUS

(chem-climate)

CURRENT GEOS-CHEM MODEL CAPABILITIES

• Goddard Earth Observing System (GEOS) global assimilated meteorological data, 1983-present including forecasts
• TPCORE advection, GEOS convective mass flux and PBL diagnostics
• Resolution: 1^ox1^o-^-4^ox5^o horizontal, 20-72 layers in vertical, nested capability → 1^ox1^o
• Mature applications:
• Tropospheric O₃-NO_x-VOC chemistry
• Aerosols coupled to chemistry
• CO₂, CH₄
• Oxygenated organics, nitriles, methyl iodide
• Under construction:
• fvDAS simulation capability (for 11/02-present)
• Linkage to CMAQ regional model
• Stratospheric chemistry
• Mercury
• Methyl bromide, chloride
• Linkage to chemical data assimilation at GMAO
• Planned:
• Aerosol microphysics
• Coupling to GISS GCM meterological fields
• Hydrogen
• POPs

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GEOS-CHEM DEVELOPMENT APPROACH

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• Close association with NASA Global Modeling & Assimilation Office (GMAO)
• use GMAO/GEOS meteorological data sets and transport schemes
• Model versions updated frequently to keep up with state of science and to increase traceability
• benchmarking of code, single gatekeeper (Bob Y.) to minimize errors
• users encouraged to update to latest version as they can. No dedicated effort to support old versions.
• Encouragement of multi-institutional user community, user-friendliness, support
• free distribution of code to competent users
• users’ guide
• web site
• Bob Yantosca

VISION FOR GEOS-CHEM

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• A “living CTM” focused on pushing the frontiers of knowledge of global atmospheric composition
• “living CTM” , “pushing the frontiers” means nimble and vigorous approach to code development and update
• ““global” as opposed to “regional”
• “atmospheric composition” in the broadest sense
• A tool for supporting other activities:
• assessments (GMI)
• satellite retrievals (NASA, CSA, ESA)
• regional air quality models (CMAQ)
• data assimilation (GMAO)
• climate models (GISS)

How is this to be supported?

• GEOS-CHEM is a grass-roots model. It needs to be supported by its community (“consortium” a better word?): user participation, ownership, responsibility, feedback are essential
• Central management can be provided by Harvard (Jacob/Yantosca) for foreseeable future

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A PROPOSED MANAGEMENT CHARTER FOR GEOS-CHEM�

• Model scientist (Jacob) is responsible in consultation with users for
• code integrity
• development prioritization
• relationships in user community, issues of general benefit
• admission of new users
• Model programmer (Yantosca) is responsible for
• maintenance of standard version
• code updates
• user support
• interface with GMAO
• Users are responsible for
• maintaining communication with other users (web site)
• updating regularly to latest version of model
• giving credit to developers in publications
• not distributing code
• Developers are responsible for
• providing codes and data sets (when mature) for implementation in standard version
• working with model programmer in this implementation
• updating to new standard version (no growing parallel versions of code!)

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