NOCS ORCA1 home page

The NOCS ORCA1 home page

Welcome to the NOCS ORCA1 information service

These pages contain an ever-increasing collection of resources relating to the ORCA R1 configuraton of the NEMO model. This configuration has been constructed in collaboration with the UK Met. Office and uses a grid which, in the tropics, is close to that used in HadGOM1, the ocean component of the coupled model HadGEM1

At NOCS the ORCA R1 configuration (aka ORCA1) is used in 'ocean-only' mode forced by high frequency atmospheric fields from the NCAR Common Ocean Reference Experiments (CORE) data collection.

The ORCA R1 grid has been carefully constructed to ensure it is a compliant member of the ORCA family. That is it has a tripolar grid with poles at the same locations as the ORCA R2, R05 and R025 grids. The meridional scale factors are also related such that outside of the tropics:

e2t(ORCA_R1) ~ 2*e2t(ORCA_R05)

ORCA R1 differs from its higher resolution siblings between 19.6058° S and 19.6058° N. Between these latitudes the meridional grid spacing is smoothly varied down to a minimum of around 1/3° at the equator with a near-constant spacing within 3° of the equator. This arrangement allows a better representation of tropical waves. This tropical refinement is superimposed on a meridional grid-spacing which varies according to the cosine of the latitude with a base resolution of 1° . The meridional grid spacing (in metres) along a typical N-S line (i=181) is shown below; the equator lies at y=146:

The grid definition file, bathymetry and initial fields for the ORCA1 model can be obtained from our configurations and download page. Additional pages, which can be accessed via the pull-down menus at the top, contain detailed descriptions of the pre- and post- processing steps that we undertake with the NEMO model at NOCS.