1. SECOND GEOS-CHEM USERS’ MEETING April 4-6, 2005 Thanks to NASA/ACMAP and HUCE for providing travel support! Meeting objectives: To share model experiences To guide model direction and define model development needs To meet each other and develop collaborations The GEOS-CHEM user community

2. MEETING AGENDA Monday April 4 –Model overview (9-10:30) –Global tropospheric chemistry (10:45-12:15) –Global aerosols (1:15-3:30) –Intercontinental transport (4-5:30) –5:30: reception Tuesday April 5 –Inverse modeling of emissions: CO and CO 2 (9-10:45) –Inverse modeling of emissions: NO x and VOCs (11:15-12:45) –Expanding model capabilities (2-3:30) –Regional air quality (4-5:30) Wednesday April 6 –Global chemical budgets (9-11) –Model issues and directions (11:15-3)  Schedule is tight and must be enforced by the chairs – please allow time for questions within your time slot!  We will project all presentations from a common PC; please email your presentations to Chris Holmes (cdh@io.harvard.edu) or give them to him during the break before your sessioncdh@io.harvard.edu  Presentations will be posted on meeting web site unless you object

3. GEOS-CHEM: global chemical transport model (CTM) of atmospheric composition Solve for concentration vector n on global Eulerian grid with winds U and other meteorological variables input to the model Regional applications: 1-way nesting or interface with independent regional model (e.g., CMAQ)…eventually 2-way nesting Couple to dynamics (chemistry-climate and data assimilation applications) using 1-D version of model (ongoing work at Harvard and NASA/GMAO): GCM including tracer transport GCM including tracer transport 1-D (column) GEOS-CHEM: integrate over  t 1-D (column) GEOS-CHEM: integrate over  t Meteorological and chemical data assimilation Meteorological and chemical data assimilation Couple over model time step  t

4. CURRENT GEOS-CHEM CAPABILITIES Goddard Earth Observing System (GEOS) global assimilated meteorological data, 1983-present; GISS GCM 3 meteorological data Resolution: 1 o x1 o - - 4 o x5 o horizontal, 20-72 layers in vertical, nested capability  1 o x1 o, linkage to CMAQ regional model Open-MP parallelization Mature applications: –Tropospheric ozone and aerosol chemistry –CO 2, CH 4 –Mercury –Oxygenated organics, nitriles, methyl halides… Under construction: –1-D version (Harvard/GMAO) –Model adjoint (Caltech/Harvard/JPL/UT) –MPI parallelization (JPL) –Stratospheric chemistry (l’Aquila) –Aerosol microphysics (CMU) –Aerosol phase transitions (Harvard) –Hydrogen (UW) –POPs (CSIC-Barcelona)

5. VISION FOR GEOS-CHEM A CTM focused on pushing the frontiers of knowledge of global atmospheric composition –“pushing the frontiers” means nimble and vigorous approach to code development and update –“atmospheric composition” in the broadest sense –development is guided by grass-roots scientific needs A tool for supporting other activities: –assessments (GMI) –satellite retrievals –regional air quality models (CMAQ) –data assimilation (GMAO) –climate models (GISS) How is this supported? –GEOS-CHEM is a cooperative model, owned and supported by its user community. User participation, ownership, responsibility, feedback are essential –Management is supported by NASA (1 FTE, Bob Y.). Keep management cost low and scientific return high through user participation.

6. FUNCTIONING OF GEOS-CHEM COMMUNITY Model Scientist (Jacob) is responsible for code integrity development prioritization relationships in user community, issues of general benefit admission of new users Model Engineer (Yantosca) is responsible for version control, code updates user support interface with GMAO Users are responsible for maintaining communication with other users (web site, users’ meeting) updating regularly to latest version of model not distributing code providing mature new codes and data sets for implementation in standard model giving credit to recent developers through coauthorships in publications being resourceful

7. WHAT’S IN A NAME? “GEOS-CHEM” is not a proper acronym, it should be “GEOS-Chem”. Do we care? It’s also long to write, is “GC” an acceptable acronym for an improper acronym?