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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

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

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

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)

The UK is moving towards a more coordinated approach based on the NEMO model
  • This forms the core of “OCEANS 2025” with plans for (amongst others):
  • Global 1/4o models with biogeochemistry and 1/12o nested regions
  • Global 1/12o physics only model by 2010
Theme 9: NOCS NEMO activities
  • 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

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)

Current status of Drakkar configurations
  • at NOCS
  • Steven Alderson, Andrew Coward, Beverly de Cuevas, Adrian New, George Nurser, Yevgeny Aksenov, Jeff Blundell, Jeremy Grist
n025 100 run nocs
N025_100 run (NOCS)
  • 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

N025_100 1958 - 1975

ORCA025_G70 1958 - 2004

nocs plans for 2008
NOCS plans for 2008
  • 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

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





T/S data

NEMO conversion to AGRIF









interface routines



Further work
  • Continuity across restart files
  • Higher resolution run (standard mpi_send)
  • Blanking of areas (e.g. Pacific)
  • AGRIF with biogeochemical models
  • Southern Ocean region