Ocean circulation and Tropical Variability in the Coupled Model ECHAM5/MPI-OM.

Jungclaus, J. H., Keenlyside, Noel, Botzet, M., Haak, H., Luo, J.-J., Latif, Mojib , Marotzke, J., Mikolajewicz, U. and Roeckner, E. (2006) Ocean circulation and Tropical Variability in the Coupled Model ECHAM5/MPI-OM. Open Access Journal of Climate, 19 (16). pp. 3952-3972. DOI 10.1175/JCLI3827.1.

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Abstract

This paper describes the mean ocean circulation and the tropical variability simulated by the Max Planck Institute for Meteorology (MPI-M) coupled atmosphere–ocean general circulation model (AOGCM). Results are presented from a version of the coupled model that served as a prototype for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) simulations. The model does not require flux adjustment to maintain a stable climate. A control simulation with present-day greenhouse gases is analyzed, and the simulation of key oceanic features, such as sea surface temperatures (SSTs), large-scale circulation, meridional heat and freshwater transports, and sea ice are compared with observations.

A parameterization that accounts for the effect of ocean currents on surface wind stress is implemented in the model. The largest impact of this parameterization is in the tropical Pacific, where the mean state is significantly improved: the strength of the trade winds and the associated equatorial upwelling weaken, and there is a reduction of the model’s equatorial cold SST bias by more than 1 K. Equatorial SST variability also becomes more realistic. The strength of the variability is reduced by about 30% in the eastern equatorial Pacific and the extension of SST variability into the warm pool is significantly reduced. The dominant El Niño–Southern Oscillation (ENSO) period shifts from 3 to 4 yr. Without the parameterization an unrealistically strong westward propagation of SST anomalies is simulated. The reasons for the changes in variability are linked to changes in both the mean state and to a reduction in atmospheric sensitivity to SST changes and oceanic sensitivity to wind anomalies.

Document Type: Article
Keywords: Climatology; ANTARCTIC CIRCUMPOLAR CURRENT, SEA-SURFACE TEMPERATURE, CLIMATE SYSTEM MODEL, GLOBAL OCEAN, EL-NINO, EQUATORIAL PACIFIC, HEAT TRANSPORTS, FRESH-WATER, ICE MOTION, ATMOSPHERE
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Refereed: Yes
Open Access Journal?: No
Publisher: AMS (American Meteorological Society)
Projects: CLIVAR, DEKLIM
Date Deposited: 03 Dec 2008 16:52
Last Modified: 23 Aug 2017 09:11
URI: https://oceanrep.geomar.de/id/eprint/3872

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