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Experiences and expectations of NEMO. Andrew C. Coward, Steve Alderson and Beverly de Cuevas. Benefits of NEMO: Curvilinear grids - tripolar. NEMO Users meeting : Thursday 22nd (afternoon) and Wednesday 23rd (morning) May 2007 ・ Coupled models CICLE project at the CNRM - M. Lucas

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Experiences and expectations of nemo

Experiences and expectations of NEMO

Andrew C. Coward, Steve Alderson and Beverly de Cuevas

  • NEMO Users meeting : Thursday 22nd (afternoon) and Wednesday 23rd (morning) May 2007・

  • Coupled models

  • CICLE project at the CNRM - M. Lucas

  • MERSEA project and ECMWF system 4 prototype - A. Troccoli

  • First analyses of the new version of the sintex-F coupled model - C. De Boyer Montegut

  • Progress on incorporating NEMO into the next Met Office climate model - C. Harris

  • Grid computing with ARPEGE-NEMO coupled model - E. Maisonnave

  • Operational Oceanography

  • UK operational ocean forecasting with NEMO - A. Sellar

  • 1/12。 ocean simulations with Mercator configurations - Y. Drillet

  • The MERSEA/Mercator Ocean global 1/4。 analysis and forecasting system V2 : first results - G. Garric

  • Implementing NEMO in the new version of the Mediterranean Forecasting Sytem - S. dobricic for P. Oddo

  • Biogeochemistry of the ocean

  • Iron and C13 in NEMO-PISCES - A. Tagliabue

  • Biowaves project: first results from coupled physical/biogeochemical simulations in the N. Atlantic - G. Charria

  • Modeling the neodymium isotopic composition with the NEMO global ocean circulation model - T. Arsouze

  • Evidence for strong submesoscale variability of pCO2 in the northeast Atlantic Ocean - L. Resplandy

  • Developments / Portability

  • LIM3 a new sea ice model coupled to OPA - M. Vancoppenolle

  • Toward an alternative to the Leap Frog time stepping - M. Leclair

  • Impact of optimized calculation of Coriolis terms in the Mediterranean model set-up - S. dobricic

  • An update on the OASIS coupler development - S. Valcke

  • Dynamics of the ocean

  • Decadal variability of oxygen, temperature and salinity in mode and intermediate waters - J. Clark

  • SSS sensitivity in the Eastern North Atlantic subtropical gyre - B. Mourre

  • Diagnosis of IGW in an OGCM : an intercomparison between numerical simulations and in situ-measurements - X. Levaillant (pdf)

  • Diagnosing the ocean control on the seasonal migration of the MarineITCZ - A. Lazar

OCEANS 2025: Themes and selected scientific objectives 23rd (morning) May 2007

Theme 9: Next Generation Ocean Prediction Systems:

  • How sensitive are climate models to the manner in which sea ice is coupled?

  • Can nested models be trusted to give accurate results?

  • Can an ocean model be made energetically self-consistent?

  • What is the most appropriate level of complexity of biogeochemical models in climate studies?

    Approaches and methodologies:

  • Develop NEMO as the core OGCM for use by the scientific community in the UK,

    at resolutions of 1°, ¼°and 1/12°, and with nested grids (WP 9.10).

  • Develop an ocean model testbed permitting objective intercomparison and validation of a range

    of ecosystem models, with a view to embedding the most promising in OGCMs (WP 9.11).

OCEANS 2025: Themes and selected scientific objectives 23rd (morning) May 2007

Theme 2: Marine Biogeochemical Cycles

  • To determine the sensitivity to future climate change of the mechanisms sustaining total nutrient

    supply to the photic zone over the three major biomes of the North Atlantic.

    Approaches and methodologies:

  • Quantify the magnitude and sensitivity of nutrient fluxes associated with winter overturning

    and Ekman pumping. For overturning, this will be achieved using time-series stations,

    Argo floats and mooring data together with previous studies and basin-scale simulations

    (NEMO both at ¼º and with a smaller scale nested component at 1/12º in the North Atlantic).

OCEANS 2025: Themes and selected scientific objectives 23rd (morning) May 2007

Theme 1: Climate, Ocean Circulation, and Sea Level

  • Model simulations of climate change in the ocean

  • Identifying the causes of recent climate change in the ocean

  • Physical-biogeochemical budgets and mixing in the Southern Ocean (DIMES)

    Research plan and deliverables:

  • 2008: Completed simulation of changes in the ocean over the period 1950 - 2006 obtained by

    running NEMO globally at 1/4° resolution (and with a nested 1/12° North Atlantic grid)

    using NCEP/NCAR (and possibly ECMWF) derived surface flux fields (WP 1.1b)

  • Theme 9: NOCS NEMO activities on the NEMO model

  • Produced global 1 degree NEMO configuration (ORCA1) [shared with UKMO]

  • Tested ORCA1 with “LOBSTER” NPZD model, about to test new NOCS biogeochemistry model “MEDUSA”

  • Developed “interpolation on the fly” option for handling surface forcing fields

  • Constructed ORCA1 forcing datasets which are compatible with those used with the current DRAKKAR (global 1/4o) model

  • Completed multi-decadal integrations of ORCA025

  • Developed capability to run AGRIF nests in sea-ice regions

Performance on the NEMO model

ORCA1: 15 processors : 3.59s per timestep (2.75yrs/day)

ORCA1: 30 processors : 1.97s per timestep (5yrs/day)

ORCA1: 32 processors with LOBSTER : 3.57s per timestep

ORCA025: 56 processors: Avg ts = 14.2634 ( 9 entries ) Min = 12.016 Max = 28.412



ORCA025: 221 processors: Avg ts = 2.44 ( 14400 entries ) Min = 2.13 Max = 7.533


16 processors 1.5s per timestep (~ 7 years/day)

64 processors 4.5s per timestep (~ 0.6 years/day)

512 processors 7.2s per timestep (~0.12 years/day)

N025 100 run nocs
N025_100 run (NOCS) on the NEMO model

  • Drakkar code with DFS3 forcing

  • On-line interpolation of atmospheric fields

  • cdmp = 0.0333 (5 times weaker than G70)

  • icedmp = 25 (same as G70)

  • 1958 - 2004 (currently1997)

Drake passage and bering strait transport comparison

Drake Passage and Bering Strait transport comparison on the NEMO model

N025_100 1958 - 1975

ORCA025_G70 1958 - 2004

Nocs plans for 2008
NOCS plans for 2008 on the NEMO model

  • Complete and analyse N025_100

  • Investigate CICE vs LIM3

  • Extend tests with AGRIF in North-west Atlantic

  • Run ORCA025 with biogeochemistry

Experiments with agrif at nocs

Experiments with AGRIF at NOCS on the NEMO model

Oceans 2025

Steven Alderson

Work Package 2.5:

“… NEMO will be run globally at 1/4° with biogeochemistry and with a higher resolution 1/12° nested model ….”

AGRIF nesting on the NEMO model





T/S data

NEMO conversion to AGRIF on the NEMO model









interface routines



Schematic for calculation of fluxes at water surface on the NEMO model

Outer model

Nest (modified)

1° model vs order-3 nest in 1° model: SST (4mnth) on the NEMO model




Further work on the NEMO model

  • Continuity across restart files

  • Higher resolution run (standard mpi_send)

  • Blanking of areas (e.g. Pacific)

  • AGRIF with biogeochemical models

  • Southern Ocean region