Developments in the UK Met Office Shelf Seas Forecasting ...godae-data/OceanView/Events/...North West Shelf System - AMM7v9 UK Met Office is the CMEMS MFC responsible for the NWS providing

Developments in the UK Met Office

Shelf Seas Forecasting System

Robert King

Enda O’Dea, Jennifer Graham,

Marina Tonani, Niall McConnell, Peter Sykes, Christine Pequignet

James While, Matt Martin, David Ford

Huw Lewis, JuanMa Castillo, Alex Arnold.

COSS-TT, Madrid, Sept. 2018

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

1. Recent history – developments to 7km resolution system (AMM7).

2. Upcoming changes – new 1.5km resolution system (AMM15).

3. Future developments – plans for coupling, DA, ensembles.

Contents

Overview - assimilation - resolution – coupling – future - summary

North West Shelf System - AMM7v9

UK Met Office is the CMEMS MFC responsible for the NWS

providing

• Daily analyses and 7-day forecasts of physical variables

• BGC forecasts (coupled with ERSEM)

• 30-year regional reanalysis

Ocean model uses NEMOv3.6 in the AMM7 configuration

• 7km resolution, 51 vertical sigma-levels, non-linear free surface

• Tidal, wind- and pressure-forced model

• Forced by Met Office NWP fluxes (hourly winds, 3hrly pressure

• LBCs from Met Office 1/12⁰ North Atlantic Model and Baltic MFC

• Climatological rivers


North West Shelf System - AMM7v9

Data assimilation scheme uses NEMOVAR

• 3DVar FGAT with 24-hour window

• Multi-scale background errors, multivariate balance

• Assimilate SST, T/S profiles, SLA

• L2/L3 SST - METOP, AVHRR, SEVIRI, VIIRS

• In situ SST - ships, drifters, mooring

• T/S profiles - XBTs, CTDs, Argo, marine mammals, gliders

• SLA from Jason-3, AltiKa, Cryosat, Sentinal 3A

• Bias correction scheme for SST and SLA

• Increments are applied using IAU method over 24hr window

• BGC – unbalanced Chl assimilation in reanalysis, will be

assimilated operationally soon.


Recent Updates: AMM7v9 (oper since Apr 2017)

Example coverage of satellite altimeter observations

for 1-month from Sentinal-3, Jason-3, Cryosat and

AltiKa (top) and those assimilated (bottom). Example monthly coverage of T/S

Temperature

profiles

Salinity

profiles

Example daily coverage of SST obs


Left: Mean surface currents for

January 2015 from AMM7v8 and

v9 and from observation-derived

current products.

Right: Depth profile of

temperature (left) and salinity

(right) innovation statistics from

AMM7 v8 (grey) and v9 (black)

averaged over full domain and 2-

year period.

King et al., 2018, Ocean Modelling

New system with assimilation of SST, SLA, and T/S profiles

Large reduction (>25%) in T/S RMS errors compared to v8 system.

Assimilation of SLA also introduces eddy-scale features to our analyses

which compares well with altimeter-derived surface current estimates.

Temperature Salinity

OLD

NEW

OLD

NEW

--- mean error

— RMSE

Recent History: AMM7v9 (oper since Apr 2017)


Upcoming changes: AMM15

AMM15

AMM7


Recently upgrading the ocean model component to the 1.5km

resolution AMM15.

Higher resolution, slightly smaller domain.

New, higher resolution EMODnet bathymetry and coastline.

Surface forcing now used ECMWF bulk fluxes.

No change in vertical resolution.

Allows for fine detail of flow speed and variability, and can now begin

to resolve mesoscale eddies and internal tides.

Off-shelf biases are reduced, but on-shelf biases remain relatively

unchanged.

Graham et al., 2018, GMD


Recently upgrading the ocean model component to the 1.5km

resolution AMM15.

Higher resolution, slightly smaller domain.

New, higher resolution EMODnet bathymetry and coastline.

Surface forcing now used ECMWF bulk fluxes.

No change in vertical resolution.

Allows for fine detail of flow speed and variability, and can now begin

to resolve mesoscale eddies and internal tides.

Off-shelf biases are reduced, but on-shelf biases remain relatively

unchanged.

Graham et al., 2018, GMD



Recently upgrading the ocean model component to the 1.5km resolution AMM15.

Reduced biases in deep water regions going from AMM7 to AMM15, but on-shelf biases are mostly

unchanged as vertical processes dominate in shallow water.

AMM7

AMM15


AMM7

AMM7

AMM15

AMM15

SST (°C)

1st Feb 2016

Upcoming changes: AMM15 with assimilation

AMM15 assimilation

follows same approach

as for AMM7

Assimilation of satellite

and in situ SST data,

satellite altimeter SLA

data (in the deep part of

the domain), and in situ

temperature/salinity

profiles has been

implemented in AMM15

Retains high resolution

model information.


AMM15+DA vs AMM7+DA

SST

AMM15+DA

AMM7+DAAMM15+DA

AMM7+DA

S profilesT profiles

SLA mean bias

AMM7

AMM15


AMM7 AMM15

AMM15+DA vs AMM7+DA


Comparison to independent glider observations (Orkney-Faroes).

Fresh salinity bias and subsurface cool bias in model reduced (AMM7 -> AMM15)

Likely to be due to a combination of assimilation and model improvements.

Obs-model

T profiles

Obs-model

S profiles

OCEAN

ATMOSPHERE WAVES

Bottom stress

SEDIMENTS/BIOGEOCHEM

Surface stress

Wind

LAND SURFACE

Freshwater, Nutrients, Temperature

Surfacefluxes

Radiation, Temp, Precip, Evap

Towards coupled prediction?

Monthly-mean impact of wave forcing on SST – difference between ocean-wave and ocean-only

April 2014 July 2014 Oct 2014 Feb 2015

Sensitivity of SST to wave coupling (without assimilation)

Inclusion of wave processes tend to cool simulated sea surface temperature

by order 0.5 K relative to ocean-only configurations during spring, summer

and autumn periods.


Impact of coupling ocean to atmosphere and/or wave model

(without assimilation)

Improved flux forcing provided through a fully coupled ocean-wave-

atmosphere system can lead to systematic improvement of ocean sea

surface temperature simulations for the North West Shelf region.

ocean-only ocean-wave atm-ocean atm-ocean-wave


Monthly-mean impact on SST – difference to OSTIA SST analysis

2018/19:

• Test changes to vertical mixing and light attenuation schemes.

• Test new high resolution altimeter observations.

• Estimate new error co-variances for AMM15.

• Implement coupled ocean-wave system operationally.

• Continue testing Chl PFT assimilation.

• Assimilate optical properties and test multivariate BGC

assimilation

2019-2021:

• Upgrading DA to work with NEMO4.0 and wetting-and-drying.

• Prepare for SWOT – swath altimeter.

• Investigate assimilation of altimeter SLA data in shallower waters.

• Continue testing fully coupled UKEP system

• Investigate impact of physical DA on BGC

• Ensemble forecasts and ensemble DA.

Future Developments


Summertime surface and bottom temperature

sensitivity to vertical mixing and light

attenuation scheme.

Summary

Significant impact of assimilation of SLA and profiles into operational AMM7

- limited by spatial and temporal sampling of sub-surface obs

Upgrading to a higher resolution model (AMM15)

- lack of observations hinders validation

Existing assimilation capability has been implemented in AMM15

- operational later this year

From next year will couple AMM15 to wave model.

- again hindered by lack of (ocean and surface flux) observations

Lots of developments planned over coming few years.


Developments in the UK Met Office Shelf Seas Forecasting ...godae-data/OceanView/Events/...North West Shelf System - AMM7v9 UK Met Office is the CMEMS MFC responsible for the NWS providing

Documents