The CO5 configuration of the 7 km Atlantic Margin Model: large-scale biases and sensitivity to forcing, physics options and vertical resolution

Abstract

Abstract. We describe the physical model component of the standard Coastal Ocean version 5 configuration (CO5) of the European north-west shelf (NWS). CO5 was developed jointly between the Met Office and the National Oceanography Centre. CO5 is designed with the seamless approach in mind, which allows for modelling of multiple timescales for a variety of applications from short-range ocean forecasting to climate projections. The configuration constitutes the basis of the latest update to the ocean and data assimilation components of the Met Office's operational Forecast Ocean Assimilation Model (FOAM) for the NWS. A 30.5-year nonassimilating control hindcast of CO5 was integrated from January 1981 to June 2012. Sensitivity simulations were conducted with reference to the control run. The control run is compared against a previous non-assimilating Proudman Oceanographic Laboratory Coastal Ocean Modelling System (POLCOMS) hindcast of the NWS. The CO5 control hindcast is shown to have much reduced biases compared to POLCOMS. Emphasis in the system description is weighted to updates in CO5 over previous versions. Updates include an increase in vertical resolution, a new vertical coordinate stretching function, the replacement of climatological riverine sources with the pan-European hydrological model E-HYPE, a new Baltic boundary condition and switching from directly imposed atmospheric model boundary fluxes to calculating the fluxes within the model using a bulk formula. Sensitivity tests of the updates are detailed with a view toward attributing observed changes in the new system from the previous system and suggesting future directions of research to further improve the system.

AMM15: a new high-resolution NEMO configuration for operational simulation of the European north-west shelf

“…Off-shelf, AMM7 was found to alternate between a cold bias in the winter months and warm bias in the summer (June, July, August; JJA; O'Dea et al, 2017). For AMM15 the model has a relatively small bias off-shelf for the majority of the year, with the exception in JJA when a similar warm bias remains.…”

“…1). However, aside from the horizontal grid, AMM15 shares many features with the previous configuration, which has been described in O'Dea et al (2012O'Dea et al ( , 2017. Here we outline some of the key components and parameterizations.…”

“…This also neglects the additional impact of suspended sediment. The scheme tested by O'Dea et al (2017) uses a single-band light attenuation scheme in which the depth of penetration varies with the depth of bathymetry. While this scheme may be appropriate for regions of the North Sea where depth is likely proportional to the water clarity, it does not account for high chlorophyll concentrations in deeper, nutrient-rich waters, such as the Norwegian Trench and the north-east Atlantic.…”

Challenging Vertical Turbulence Mixing Schemes in a Tidally Energetic Environment: 1. 3‐D Shelf‐Sea Model Assessment

“…We found that the sensitivity of models to mixing schemes and choice of limiters is comparable to the sensitivity to horizontal resolution (Graham et al, 2018) and surface flux formulation (O'Dea et al, 2017).…”

“…10.1029/2018JC014307Journal of GeophysicalResearch: Oceans et al, 2018;O'Dea et al, 2017) demonstrate persistent strong warm biases of benthic temperatures in this region, comparing with observations. In our analysis, we examine how local properties of the pycnocline are related to simulation errors in bulk characteristics.…”