GO5.0: the joint NERC–Met Office NEMO global ocean model for use in coupled and forced applications

Abstract

Abstract. We describe a new Global Ocean standard configuration (GO5.0) at eddy-permitting resolution, developed jointly between the National Oceanography Centre and the Met Office as part of the Joint Ocean Modelling Programme (JOMP), a working group of the UK's National Centre for Ocean Forecasting (NCOF) and part of the Joint Weather and Climate Research Programme (JWCRP). The configuration has been developed with the seamless approach to modelling in mind for ocean modelling across timescales and for a range of applications, from short-range ocean forecasting through seasonal forecasting to climate predictions as well as research use. The configuration has been coupled with sea ice (GSI5.0), atmosphere (GA5.0), and land-surface (GL5.0) configurations to form a standard coupled global model (GC1). The GO5.0 model will become the basis for the ocean model component of the Forecasting Ocean Assimilation Model, which provides forced short-range forecasting services. The GC1 or future releases of it will be used in coupled short-range ocean forecasting, seasonal forecasting, decadal prediction and for climate prediction as part of the UK Earth System Model.A 30-year integration of GO5.0, run with CORE2 (Common Ocean-ice Reference Experiments) surface forcing from 1976 to 2005, is described, and the performance of the model in the final 10 years of the integration is evaluated against observations and against a comparable integration of an existing standard configuration, GO1. An additional set of 10-year sensitivity studies, carried out to attribute changes in the model performance to individual changes in the model physics, is also analysed. GO5.0 is found to have substantially reduced subsurface drift above the depth of the thermocline relative to GO1, and also shows a significant improvement in the representation of the annual cycle of surface temperature and mixed layer depth.

Explicit representation and parametrised impacts of under ice shelf seas in the <i>z</i><sup>∗</sup> coordinate ocean model NEMO 3.6

“…3a). With variable vertical resolution (I_31L, I_46L and I_75L), such as is typically used in global configurations of NEMO (Timmermann et al, 2005;DRAKKAR group, 2007;Megann et al, 2014), the coarsest resolution in the cavity seems to determine the total melt. This is because more than 50 % of the melting occurs between 500 and 700 m depth where the resolution is coarsest (not shown).…”

“…The bathymetry used for the model domain north of the Antarctic continental shelf is that described by Megann et al, (2014). Over the Antarctic continental shelves the IBCSO dataset (Arndt et al, 2013) is used.…”

The effect of model bias on Atlantic freshwater transport and implications for AMOC bi-stability

“…This model configuration is also used in the operational seasonal and decadal forecast systems of the Met Office (GloSea5 and DEPRESYS3). The ocean model is the Global Ocean 5.0 (Megann et al, 2014) version of the v3.4 NEMO model (Madec, 2008) and uses the ORCA025 tripolar grid configuration. It has 75 vertical levels, and a nominal horizontal resolution of 0.25 degrees (compared to the typical 1 degree resolution of the CMIP5 models).…”

AMM15: A new high resolution NEMO configuration for operational simulation of the European North West Shelf

“…For operational purposes, boundary conditions will be derived For 1985For -1989, the boundaries used here come from a free running global ocean hindcast (Megann et al, 2014). For 1990 onwards, the boundary conditions are taken from the Global Seasonal Forecast System (GLOSEA), version 5 (MacLachlan et al, 2015;Jackson et al, 2016), which includes assimilation of both satellite and in situ observations, where available.…”