AMM15: Next generation ocean forecast model for the UK ... · • Validation of new configuration (Graham et al. 2018, GMD). • 30 year control simulation, comparison with existing

AMM15: Next generation ocean forecast

model for the UK shelf seas

Jennifer Graham(and many others)

NPOP, 15-17 May 2018

www.metoffice.gov.uk © Crown Copyright 2017, Met Office

AMM: Atlantic Margin Model


Regional configuration of the NEMO ocean model, covering European NW Shelf.

• Some differences to the global ocean configurations include:

• Boundary forcing

• Terrain-following coordinates (S-levels)

• Tidal forcing

• Choice of parameterisations

• Current operational system based on: AMM7 = Atlantic Margin Model, 7 km resolution

• O’Dea et al., 2017, GMD

• Next generation system, increased horizontal resolution: AMM15 = 1.5 km resolution

• Graham et al., 2018, GMD


AMM15: Atlantic Margin Model, 1.5 km

resolution

• Regional configuration of NEMO ocean

model (v 3.6).

• Higher resolution, slightly smaller domain.

• New, higher resolution bathymetry and

coastline.

• EMODnet: European Marine Observation

and Data Network.

• AMM7 bathymetry based on NOOS: NW

Shelf Operational Oceanographic System.

Note: no change in vertical resolution (both have

51 S-levels.)

AMM15: NW Shelf

AMM7

AMM15: Model description • Validation of new configuration (Graham et al. 2018, GMD).

• 30 year control simulation, comparison with existing operational system (O’Dea et al., 2017).

• Free running simulation, no data assimilation.

• Boundary forcing:

• Global ocean reanalysis, available from seasonal forecasting system (GLOSEA NEMO configuration, ~ 1/4 deg

resolution).

• Baltic boundary data provided from GETM regional configuration developed at IOW (~ 1/60 deg resolution).

• Boundary forcing includes full depth T, S, SSH and barotropic U,V.

• Tides: TPXO7.2, Atlantic model.

• Surface forcing: ERA-Interim, CORE bulk forcing algorithm.

• River runoff: Climatology based on ~ 30 years of daily gauge data.

• Parameterisations:

• Majority consistent between AMM7 and AMM15, except reduced lateral diffusion (due to resolved mixing

processes).


High resolution allows for fine scale

detail of flow speed and variability.

Improved bathymetry, and improved

physics.

EMODnet data – high resolution

bathymetry and coastline.


Initial results

Improved bathymetry: impact on tides, topographic steering, mixing etc.

Note: both models use 51 σ-levels (Siddorn & Furner, 2013).

AMM7 AMM15

Initial results


Similarly, we resolve fine scale

detail of density structure –

temperature and salinity.

Increased submesoscale activity

across domain.

April – June, seasonal transition.

SST


Sub-surface VariabilityTemperature cross-section

west of Lewis.

Variability on scale ~ 10km



AMM15 Validation


• Seasonal SST anomalies: Comparison with OSTIA (satellite observations,

1991-2010).• Reduced overall bias in AMM15 compared to AMM7, but improvement is greater off-shelf.


• Bottom temperature anomalies: Comparison with EN4 (in-situ observations).• Some improvement in AMM15, but warm bias remains.


• Seasonal SSS anomalies: Comparison with EN4 (in-situ observations).• Reduced bias in North, but increased fresh bias in Norwegian Trench.


• Biases in stratification: Comparison with EN4 (in-situ T

& S observations).

• Some improvement in AMM15,

particularly on Outer Shelf, but

biases remain elsewhere.

AMM15: Temporal variability


• Temperature variability on the shelf is similar in both AMM15 and AMM7.

• Greater differences seen in salinity – possibly due to boundary conditions?


Conclusions and future work…

Summary


New, exciting resource for understanding

shelf processes around the UK.

- Fine-scale processes not resolved in

previous configurations.

Overall improvement in climatology, but

similar biases remain on shelf

- Climate on the shelf driven predominantly

by vertical rather than horizontal

processes?

- No change in vertical resolution or

parameterisations in AMM15.

Future AMM/NEMO development


Ongoing development of AMM configurations:

- Impact of vertical processes on stratification?

- Impact of boundary conditions and/or runoff fluxes?

Further model developments:

- Wetting & drying development in NEMO (v4.0)

- Impact of coupling: pull through effort from UKEP

Operational implementation

- Addition of data assimilation

- Products available through Copernicus later this year…

Any questions?


Contact me: [email protected]

Or, to find out more:

Graham et al., 2018: AMM15: a new high-resolution NEMO configuration for operational simulation of the European north-

west shelf, Geosci. Model Dev., 11, 681-696, https://doi.org/10.5194/gmd-11-681-2018

O’Dea et al., 2017: The CO5 configuration of the 7 km Atlantic Margin Model: large-scale biases and sensitivity to forcing,

physics options and vertical resolution, Geosci. Model Dev., 10, 2947-2969, https://doi.org/10.5194/gmd-10-2947-2017

PhD project deadline 1st June: speak to me or Jeff for further details.

mailto:[email protected]

http://www.enveast.ac.uk/nexuss/nexuss-cdt-projects/-/asset_publisher/xczFrDnc3B0g/content/polton_uenv18nex-using-ocean-gliders-to-improve-prediction-of-heat-uptake-in-shelf-seas?inheritRedirect=false&redirect=http://www.enveast.ac.uk/nexuss/nexuss-cdt-projects?p_p_id%3D101_INSTANCE_xczFrDnc3B0g%26p_p_lifecycle%3D0%26p_p_state%3Dnormal%26p_p_mode%3Dview%26p_p_col_id%3Dcolumn-2%26p_p_col_pos%3D4%26p_p_col_count%3D8

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AMM15: Next generation ocean forecast model for the UK ... · • Validation of new configuration (Graham et al. 2018, GMD). • 30 year control simulation, comparison with existing