The impact of a new high-resolution ocean model on the Met Office North-West European Shelf forecasting system

Abstract. The North-West European shelf ocean forecasting system has been providing oceanographic products for the European continental shelf seas for more than fifteen years. In that time several different configurations have been implemented, updating the model and the data assimilation components. The latest configuration to be put in operations, an eddy resolving model at 1.5 km (AMM15), replaces the 7 km model (AMM7) that has been used for a number of years. This has improved the ability to resolve the mesoscale variability in this area. An overview of this new system and its initial validation is provided in this paper, highlighting the differences with the previous version. Validation of the model is based on the results of two years (2016–2017) trial experiments run with the low and high resolution systems in their operational configuration. The 1.5 km system has been validated against observations and the low resolution system, trying to understand the impact of the high resolution on the quality of the products delivered to the users. Although the number of observations is a limiting factor, especially for the assessment of model variables like currents and salinity, the new system has been proven to be an improvement in resolving fine scale structures and variability and provides more accurate information on the major physical variables, like temperature, salinity and horizontal currents. AMM15 improvements are evident from the validation against high-resolution observations, available in some selected areas of the model domain. However, validation at the basin scale and using daily means penalised the high-resolution system and does not reflect its superior performance. This increment in resolution also improves the capabilities to provide marine information closer to the coast even if the coastal processes are not fully resolved by the model.

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The impact of a new high-resolution ocean model on the Met Office North-West European Shelf forecasting system

Ocean Science ◽

10.5194/os-15-1133-2019 ◽

2019 ◽

Vol 15 (4) ◽

pp. 1133-1158 ◽

Cited By ~ 8

Author(s):

Marina Tonani ◽

Peter Sykes ◽

Robert R. King ◽

Niall McConnell ◽

Anne-Christine Péquignet ◽

...

Keyword(s):

High Resolution ◽

Data Assimilation ◽

Superior Performance ◽

North West ◽

Resolution System ◽

European Shelf ◽

Forecasting System ◽

The Impact ◽

New System ◽

West European

Abstract. The North-West European Shelf ocean forecasting system has been providing oceanographic products for the European continental shelf seas for more than 15 years. In that time, several different configurations have been implemented, updating the model and the data assimilation components. The latest configuration to be put in operation, an eddy-resolving model at 1.5 km (AMM15), replaces the 7 km model (AMM7) that has been used for 8 years to deliver forecast products to the Copernicus Marine Environment Monitoring Service and its precursor projects. This has improved the ability to resolve the mesoscale variability in this area. An overview of this new system and its initial validation is provided in this paper, highlighting the differences with the previous version. Validation of the model with data assimilation is based on the results of 2 years (2016–2017) of trial experiments run with the low- and high-resolution systems in their operational configuration. The 1.5 km system has been validated against observations and the low-resolution system, trying to understand the impact of the high resolution on the quality of the products delivered to the users. Although the number of observations is a limiting factor, especially for the assessment of model variables like currents and salinity, the new system has been proven to be an improvement in resolving fine-scale structures and variability and provides more accurate information on the major physical variables, like temperature, salinity, and horizontal currents. AMM15 improvements are evident from the validation against high-resolution observations, available in some selected areas of the model domain. However, validation at the basin scale and using daily means penalized the high-resolution system and does not reflect its superior performance. This increment in resolution also improves the capabilities to provide marine information closer to the coast even if the coastal processes are not fully resolved by the model.

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Assessing the Impact of the Assimilation of SWOT Observations in a Global High-Resolution Analysis and Forecasting System Part 1: Methods

Frontiers in Marine Science ◽

10.3389/fmars.2021.691955 ◽

2021 ◽

Vol 8 ◽

Author(s):

Mounir Benkiran ◽

Giovanni Ruggiero ◽

Eric Greiner ◽

Pierre-Yves Le Traon ◽

Elisabeth Rémy ◽

...

Keyword(s):

High Resolution ◽

Data Assimilation ◽

Companion Paper ◽

Ocean Model ◽

Data Assimilation Scheme ◽

High Resolution Analysis ◽

Resolution Analysis ◽

Forecasting System ◽

The Impact ◽

Assimilation Scheme

The future Surface Water Ocean Topography (SWOT) mission due to be launched in 2022 will extend the capability of existing nadir altimeters to enable two-dimensional mapping at a much higher effective resolution. A significant challenge will be to assimilate this kind of data in high-resolution models. In this context, Observing System Simulation Experiments (OSSEs) have been performed to assess the impact of SWOT on the Mercator Ocean and Copernicus Marine Environment Monitoring Service (CMEMS) global, high-resolution analysis and forecasting system. This paper focusses on the design of these OSSEs, in terms of simulated observations and assimilation systems (ocean model and data assimilation schemes). The main results are discussed in a companion paper. Two main updates of the current Mercator Ocean data assimilation scheme have been made to improve the assimilation of information from SWOT data. The first one is related to a different parametrisation of the model error covariance, and the second to the use of a four-dimensional (4D) version of the data assimilation scheme. These improvements are described in detail and their contribution is quantified. The Nature Run (NR) used to represent the “truth ocean” is validated by comparing it with altimeter observations, and is then used to simulate pseudo-observations required for the OSSEs. Finally, the design of the OSSEs is evaluated by ensuring that the differences between the assimilation system and the NR are statistically consistent with the misfits between real ocean observations and real-time operational systems.

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Can wave coupling improve operational regional ocean forecasts for the north-west European Shelf?

Ocean Science ◽

10.5194/os-15-669-2019 ◽

2019 ◽

Vol 15 (3) ◽

pp. 669-690 ◽

Cited By ~ 6

Author(s):

Huw W. Lewis ◽

Juan Manuel Castillo Sanchez ◽

John Siddorn ◽

Robert R. King ◽

Marina Tonani ◽

...

Keyword(s):

Sea Surface ◽

Ocean Wave ◽

Prediction System ◽

Wave Coupling ◽

North West ◽

The North ◽

European Shelf ◽

Ocean Prediction ◽

The Impact ◽

West European

Abstract. Operational ocean forecasts are typically produced by modelling systems run using a forced mode approach. The evolution of the ocean state is not directly influenced by surface waves, and the ocean dynamics are driven by an external source of meteorological data which are independent of the ocean state. Model coupling provides one approach to increase the extent to which ocean forecast systems can represent the interactions and feedbacks between ocean, waves, and the atmosphere seen in nature. This paper demonstrates the impact of improving how the effect of waves on the momentum exchange across the ocean–atmosphere interface is represented through ocean–wave coupling on the performance of an operational regional ocean prediction system. This study focuses on the eddy-resolving (1.5 km resolution) Atlantic Margin Model (AMM15) ocean model configuration for the north-west European Shelf (NWS) region. A series of 2-year duration forecast trials of the Copernicus Marine Environment Monitoring Service (CMEMS) north-west European Shelf regional ocean prediction system are analysed. The impact of including ocean–wave feedbacks via dynamic coupling on the simulated ocean is discussed. The main interactions included are the modification of surface stress by wave growth and dissipation, Stokes–Coriolis forcing, and wave-height-dependent ocean surface roughness. Given the relevance to operational forecasting, trials with and without ocean data assimilation are considered. Summary forecast metrics demonstrate that the ocean–wave coupled system is a viable evolution for future operational implementation. When results are considered in more depth, wave coupling was found to result in an annual cycle of relatively warmer winter and cooler summer sea surface temperatures for seasonally stratified regions of the NWS. This is driven by enhanced mixing due to waves, and a deepening of the ocean mixed layer during summer. The impact of wave coupling is shown to be reduced within the mixed layer with assimilation of ocean observations. Evaluation of salinity and ocean currents against profile measurements in the German Bight demonstrates improved simulation with wave coupling relative to control simulations. Further, evidence is provided of improvement to simulation of extremes of sea surface height anomalies relative to coastal tide gauges.

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Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea

PLoS ONE ◽

10.1371/journal.pone.0164482 ◽

2016 ◽

Vol 11 (10) ◽

pp. e0164482 ◽

Cited By ~ 7

Author(s):

Beatrix Siemering ◽

Eileen Bresnan ◽

Stuart C. Painter ◽

Chris J. Daniels ◽

Mark Inall ◽

...

Keyword(s):

Environmental Drivers ◽

North West ◽

The North ◽

Phytoplankton Distribution ◽

European Shelf ◽

Shelf Sea ◽

West European

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The impact of resolving the Rossby radius at mid-latitudes in the ocean: results from a high-resolution version of the Met Office GC2 coupled model

Geoscientific Model Development ◽

10.5194/gmd-9-3655-2016 ◽

2016 ◽

Vol 9 (10) ◽

pp. 3655-3670 ◽

Cited By ~ 33

Author(s):

Helene T. Hewitt ◽

Malcolm J. Roberts ◽

Pat Hyder ◽

Tim Graham ◽

Jamie Rae ◽

...

Keyword(s):

High Resolution ◽

Coupled Model ◽

Ocean Model ◽

The Body ◽

Western Boundary ◽

Coupled Models ◽

Technical Developments ◽

Enhanced Resolution ◽

Circumpolar Current ◽

The Impact

Abstract. There is mounting evidence that resolving mesoscale eddies and western boundary currents as well as topographically controlled flows can play an important role in air–sea interaction associated with vertical and lateral transports of heat and salt. Here we describe the development of the Met Office Global Coupled Model version 2 (GC2) with increased resolution relative to the standard model: the ocean resolution is increased from 1/4 to 1/12° (28 to 9 km at the Equator), the atmosphere resolution increased from 60 km (N216) to 25 km (N512) and the coupling period reduced from 3 hourly to hourly. The technical developments that were required to build a version of the model at higher resolution are described as well as results from a 20-year simulation. The results demonstrate the key role played by the enhanced resolution of the ocean model: reduced sea surface temperature (SST) biases, improved ocean heat transports, deeper and stronger overturning circulation and a stronger Antarctic Circumpolar Current. Our results suggest that the improvements seen here require high resolution in both atmosphere and ocean components as well as high-frequency coupling. These results add to the body of evidence suggesting that ocean resolution is an important consideration when developing coupled models for weather and climate applications.

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The impact of resolving the Rossby radius at mid-latitudes in the ocean: results from a high-resolution version of the Met Office GC2 coupled model

10.5194/gmd-2016-87 ◽

2016 ◽

Cited By ~ 2

Author(s):

Helene T. Hewitt ◽

Malcolm J. Roberts ◽

Pat Hyder ◽

Tim Graham ◽

Jamie Rae ◽

...

Keyword(s):

High Resolution ◽

Coupled Model ◽

Ocean Model ◽

The Body ◽

Coupled Models ◽

Surface Ocean ◽

Technical Developments ◽

Enhanced Resolution ◽

Circumpolar Current ◽

The Impact

Abstract. There is mounting evidence that resolving mesoscale eddies and boundary currents in the surface ocean field can play an important role in air-sea interaction associated with vertical and lateral transports of heat and salt. Here we describe the development of the Met Office Global Coupled Model version 2 (GC2) with increased resolution relative to the standard model: the ocean resolution is increased from 1/4° to 1/12° (28 km to 9 km at the Equator), the atmosphere resolution increased from 60 km (N216) to 25 km (N512) and the coupling frequency increased from 3-hourly to hourly. The technical developments that were required to build a version of the model at higher resolution are described as well as results from a 20 year simulation. The results demonstrate the key role played by the enhanced resolution of the ocean model: reduced Sea Surface Temperature biases, improved ocean heat transports, deeper and stronger overturning circulation and a stronger Antarctic Circumpolar Current. Our results suggest that the improvements seen here require high resolution in both atmosphere and ocean components as well as high frequency coupling. These results add to the body of evidence suggesting that ocean resolution is an important consideration when developing coupled models for weather and climate applications.

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