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 • 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 Marine ITCZ - 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)

ORCA025: 56 processors: Avg ts = 14.2634 ( 9 entries ) Min = 12.016 Max = 28.412 (0.28yrs/day)

ORCA1: 32 processors with LOBSTER : 3.57s per timestep

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)

Performance

On HECToR:

ORCA025: 221 processors: Avg ts = 2.44 ( 14400 entries ) Min = 2.13 Max = 7.533 (1.6yrs/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

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)

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

N025_100 1958 - 1975 ORCA025_G70 1958 - 2004

NOCS plans for 2008NOCS plans for 2008

Complete and analyse N025_100 Investigate CICE vs LIM3 Extend tests with AGRIF in North-west AtlanticRun ORCA025 with biogeochemistry

Complete and analyse N025_100 Investigate CICE vs LIM3 Extend tests with AGRIF in North-west AtlanticRun ORCA025 with biogeochemistry

Experiments with AGRIF at NOCSSteven AldersonSteven Alderson

Work Package 2.5:“… NEMO will be run globally at 1/4° with biogeochemistry and with a higher resolution 1/12° nested model ….”

Oceans 2025

Bathymetrydata

T/S data

Nestingtools

AGRIF nesting

NEMOAGRIF/NEMO

codeConversionroutine

AGRIFlibrary

AGRIFinterface routines

AGRIF/NEMO

NEMO conversion to AGRIF

Order-1 nest in 1° global NEMO

Order-1 nest in 1° model: surface differences (30d)

Schematic for calculation of fluxes at water surface

Outer model

Nest (modified)

Order-1 nest in 1° model: surface differences (30d)

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

longitudelongitude

latitude

No nest model vs order-3 nest in 1° model

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

Further work