Séminaire
A low-resolution version of the current climate model of the UK Met Office, HadGEM3 N96ORCA1, is presented and evaluated. It is part of the GC3.1 configuration of HadGEM3 and has got a horizontal resolution of about 130km in the atmosphere and 1° in the ocean. Requiring one order of magnitude less computing power per model year than its medium-resolution counterpart (N216ORCA025), N96ORCA1 lends itself to multi-centennial simulations and ensemble simulations, while maintaining a very high degree of traceability with N216ORCA025. On the whole, N96ORCA1 reproduces the present-day climate – mean and variability – almost as well as N216ORCA025. Geographical patterns of biases are generally very similar across the two model versions. In the North-West Atlantic, N96ORCA1 shows a cold bias because of a misrepresentation of the path of the North Atlantic Current, typical for ocean models of this resolution. In the mid-latitude Southern Ocean, the warm bias is smaller than in N216ORCA025, leading to improved ocean circulation. The simulated variability of El Niño/Southern Oscillation and the Atlantic Multidecadal Variability are close to observations. HadGEM3 GC3.1 N96ORCA1 constitutes the physical core of the UK Earth System Model (UKESM1) and will be used for many experiments for the Coupled Model Intercomparison Project 6 (CMIP6).
Julie.Deshayes@locean-ipsl.upmc.fr