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NEMO in the IPCC simulations at IPSL

NEMO in the IPCC simulations at IPSL. Sébastien Denvil IPSL Global Climate Modeling Group (IGCMG). Purpose of this talk. Overview of IPCC experiments at IPSL Technical response to IPCC requirements ORCA2-LIM specific case How big is this exercise ?. How all this came about ? (1).

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NEMO in the IPCC simulations at IPSL

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  1. NEMO in the IPCC simulations at IPSL Sébastien Denvil IPSL Global Climate Modeling Group (IGCMG)

  2. Purpose of this talk • Overview of IPCC experiments at IPSL • Technical response to IPCC requirements • ORCA2-LIM specific case • How big is this exercise ?

  3. How all this came about ? (1) • In 2002, WGCM accepted to coordinate model simulations in support of the IPCC 4th Assesment. • In 2002, WGCM agreed on a set of simulations that would be performed. • In September 2003, WGCM asked PCMDI to volunteer as a host to the database in support of IPCC Working Group I. • WGCM and PCMDI require that the simulations output conform to strict structural and metadata standards.

  4. How all this came about ? (2) • By spring, 2004, PCMDI, drew up the list of standard output fields and established the format requirements for model output. • By summer, 2004, PCMDI made available a FORTRAN library (CMOR), designed to fulfill WGCM’s requirements. • Between summer 2004 and may 2005, we ran models, rewrote output and sent it to PCMDI. • PCMDI organizes the output and makes it available via ftp and a « data portal ».

  5. NEMO AND IPSL AOGCM • IPSLCM4_v1 coupled model : • LMDZOR (96x72x19) • Climatological ozone • Direct and indirect aerosol effect • No Carbon Cycle • ORCA2-LIM configuration • No biogeochemical component • Total integration period : 2500 years. • 12 IPCC experiments.

  6. Reporting periods for requested model outputs Image from PCMDI

  7. A set of idealized simulations IPCC CO2 concentrations 4xCO2 CO 2 concentration (ppm) 2xCO2 actual 1xCO2 year Image from JL.Dufresne

  8. A set of realistic simulations Image from JL.Dufresne

  9. ROADMAP

  10. Technical response to IPCC requirements for model output • Manage large data volume • Regrid oceanic data • Rewrite netCDF output

  11. Processing structure IPSLCM4_v1 DODS / IPSL RSYNC STORAGE IDRiS / CEA

  12. IPCC requirements are stricter than CF-conventions. • Each file must contain only a single output field. • For data that are function of longitude and latitude, only grids representable as a Cartesian product of longitude and latitude axes are allowed. • Most atmospheric fields that are function of the vertical coordinate must be interpolated to standard pressure level. • The units required for the output fieds are given in the IPCC Standard Output tables. • The positive direction of vertical fluxes must be consistent with that specified on the IPCC Standard Output table « CF standard name ». • The order of array dimension must be : time, level, latitude, longitude. • If longitude is a coordinate, data must be stored west to east (in degrees), starting with the first grid point greater than or equal to 0 degrees east. • If latitude is a coordinate, data must be stored south to north (in degrees). • If there is a vertical level, data must be stored starting with the grid point nearest the surface.

  13. CMOR (Climate Model Output Rewriter) • What is it ? • Fortran code that rewrites model output. • What is it for ? • comply to extended CF-convention • help us to fulfill IPCC requirements • have fully self described files • Very efficient tool. Compulsory for the next MIP

  14. Oasis 3 /SCRIP REGRID

  15. METHOD AND TOOLS • Bicubic interpolation (as described in scrip 1.4 documentation) • With pseudo-model part of OASIS 3 : • works for scalar points only • provides « interpolation weights » • With home-made fortran routine : • adaptation to 3D case • added a loop on depth axis • adaptation to vector(U,V) case • project U and V points to T points • apply correction (change of reference)

  16. Regrid process OCEANIC FIELD OASIS3 WEIGHTS FIELDS 2D/3D T,(U,V),W point(s) F90 routine FIELDS ON REGULAR GRID

  17. How big is this exercise ? • Computational • ~30 000 hours of CPU to achieve a total of 2500 years of simulation in 9 months. • 6 dedicated processors from 2 computing centers (IDRiS/CEA-CCRT) • Data storage • 30 To of data (all inclusive) • 25% of oceanic data • 5% of ice data

  18. How much data is that ? • A single latitude/longitude map at typical climate model resolution represents about ~40 Kilobytes • If you want to look at all 10 Tbytes in the form of these latitude/longitude plots, and if • every 10 seconds you displayed another map, and if • you worked 24 hours a day 365 days each year, • You could complete the task in about 70 years. • If we divided up the task among the scientists in this room (working 50-hours weeks), each of you would have to look at a new plot every 10 seconds for 2 years.

  19. Data availability summary (as of 24 may 2005)

  20. Monthly mean ocean data availability (as of 24 may 2005)

  21. Conclusion • Bring closer model outputs and CMOR outputs • Regrid tools inside NEMO packages • CF-conventions should be able to fully describe curvilinear grids

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