Berthou et al. (2026) Km-scale regional coupled system in the Northwest European shelf for weather and climate applications: RCS-UKC4

Identification

• Journal: Geoscientific model development
• Year: 2026
• Date: 2026-09-15
• Authors: Ségolène Berthou, Juan Manuel Castillo, Vivian Fraser-Leonhardt, Sana Mahmood, Nefeli Makrygianni, Alex Arnold, Claudio Sánchez, Huw Lewis, Dale Partridge, Martin Best, Lucy Bricheno, Helen Davies, Douglas B. Clark, James R. Clark, Jeff A. Polton, Andy Saulter, Chris J. Short, Jonathan Tinker, Simon Tucker, M. J. Wright
• DOI: 10.5194/gmd-19-8535-2026

Research Groups

• Met Office, Exeter, United Kingdom
• University of Reading, Reading, United Kingdom
• School of geographical Science, University of Bristol, Bristol, United Kingdom
• Plymouth Marine Laboratory, Plymouth, United Kingdom
• National Oceanography Centre, Liverpool, United Kingdom
• UK Centre for Ecology & Hydrology, Wallingford, United Kingdom

Short Summary

This study presents an updated version of the Regional Coupled Suite – UK Coupled domain version four (RCS-UKC4), which brings corrections and enhancements relative to the UKC3 system. The RCS-UKC4 configuration includes implementation of the new Regional Atmosphere and Land configuration (RAL3.3) alongside updates to all model components relative to previous releases.

Objective

• To evaluate the impact of upgrading the atmosphere and land configuration on the coupled system, demonstrating in particular the impact on prediction of SST, winds and river discharge.
• To introduce ensemble forecasting capability and show a regional coupled system offers potential for improved ensemble wave and wind forecasting.
• To sensitivity to increasing coupling frequency to 10 min and demonstrate this enables the ability to forecast meteotsunamis.

Study Configuration

• Spatial Scale: The Northwest European shelf (NWS), which is a shallow continental shelf sea region (<250 m) where tidal energy is dissipated through strong tidal currents surrounding the British Isles.
• Temporal Scale: Weather and climate timescales, including near-real-time ensemble forecasts and climate hindcasts.

Methodology and Data

• Models used:
  • Unified Model (UM)
  • Joint United Kingdom Land Environment Simulator (JULES)
  • Nucleus for European Modelling of the Ocean (NEMO)
  • WAVEWATCH III
  • European Regional Seas Ecosystem Model (ERSEM)
• Data sources: Satellite, observation, reanalysis.

Main Results

• The new atmospheric configuration (RAL3.3) leads to warmer SSTs than RAL2, with clear improvements for May 2024, and a shift from a cold (as much as −0.5°C) night-time SST bias in June 2023 to a warm (up to 0.3°C) bias averaged over the northwest European shelf.
• The evaluation of RCS-UKC4 in marine heatwave conditions is consistent with an improved surface flux budget in RAL3.3.
• The quality of the sea surface temperature in 4-year long simulations shows acceptable biases for the SST in a free-running coupled system.

Contributions

• This study contributes to the development of regional coupled systems for weather and climate applications, demonstrating the benefits of consistent treatment of heat and momentum exchange between the atmosphere and ocean.
• The RCS-UKC4 configuration provides an improved surface flux budget and acceptable biases for the SST in a free-running coupled system.

Funding

• This research was funded by the Met Office.

Citation

@article{Berthou2026Kmscale,
  author = {Berthou, Ségolène and Castillo, Juan Manuel and Fraser-Leonhardt, Vivian and Mahmood, Sana and Makrygianni, Nefeli and Arnold, Alex and Sánchez, Claudio and Lewis, Huw and Partridge, Dale and Best, Martin and Bricheno, Lucy and Davies, Helen and Clark, Douglas B. and Clark, James R. and Polton, Jeff A. and Saulter, Andy and Short, Chris J. and Tinker, Jonathan and Tucker, Simon and Wright, M. J.},
  title = {Km-scale regional coupled system in the Northwest European shelf for weather and climate applications: RCS-UKC4},
  journal = {Geoscientific model development},
  year = {2026},
  doi = {10.5194/gmd-19-8535-2026},
  url = {https://doi.org/10.5194/gmd-19-8535-2026}
}