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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)

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Purpose of this talkPurpose of this talk

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

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How all this came about ? (1)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.

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How all this came about ? (2)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 ».

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NEMO AND IPSL AOGCMNEMO 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.

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Reporting periods for requested model outputsReporting periods for requested model outputs

Image from PCMDI

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CO

2 c

once

ntra

tion

(pp

m)

year

1xCO2

2xCO2

4xCO2

actual

IPCC CO2 concentrations

A set of idealized simulations A set of idealized simulations

Image from JL.Dufresne

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

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ROADMAPROADMAP

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Technical response to IPCC requirements for model output

Technical response to IPCC requirements for model output

Manage large data volume Regrid oceanic data Rewrite netCDF output

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Processing structureProcessing structureCoupled Model

NetCDF outputs Generate Atlas (pdf/gif)

MODIPSL

Time Series

Regrid 2D/3D

Look diagnostics

FAST/ATLAS

« CMORisation »

DODS IDRiS/CEAOff Line Diagnostics

STORAGE IDRiS / CEA

DODS / IPSL

IPSLCM4_v1

RSYNC

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IPCC requirements are stricter than CF-conventions.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.

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CMOR (Climate Model Output Rewriter)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

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Oasis 3 /SCRIP REGRIDOasis 3 /SCRIP REGRID

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METHOD AND TOOLSMETHOD 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 pointsapply correction (change of reference)

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Regrid processRegrid process

OASIS3

FIELDS 2D/3DT,(U,V),W point(s)

OCEANIC FIELD

WEIGHTS

F90 routine

FIELDS ONREGULAR GRID

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How big is this exercise ?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

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How much data is that ?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.

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

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

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ConclusionConclusion

Bring closer model outputs and CMOR outputs

Regrid tools inside NEMO packages CF-conventions should be able to

fully describe curvilinear grids