Simulation of the El Niño Southern Oscillation: Results from the Coupled Model Intercomparison Project
The El Niño Southern Oscillation (ENSO) simulations of 17 global coupled ocean–atmosphere general circulation models (CGCMs) from the Coupled Model Intercomparison Project (CMIP) are analyzed. Monthly mean values of surface air temperature, sea-level pressure and precipitation for 80 years are analyzed from control runs. Nearly half of the models studied do not employ any form of flux correction. Flux-corrected CGCMs were better at simulating the base state and annual cycle of the temperature field in the equatorial Pacific but not necessarily better at simulating ENSO variability. While a subset of the models produce realistic amplitudes of NIÑO3 and the Southern Oscillation Index (SOI), ENSO often tends to occur at a higher than observed frequency. A few models also capture the teleconnection between NIÑO3 temperature anomalies, SOI, and the global surface air temperature, sea level pressure and precipitation. Only a few models simulate phase locking of ENSO with the seasonal cycle. Most models have problems in simulating the ENSO related sea-level pressure variations over the eastern Pacific and this is associated with errors in the precipitation response. The models fall into three distinct categories based on their ability to simulate large-scale ENSO related patterns of sea-level pressure, surface air temperature and precipitation. Group 1 consists of models that represent well the Walker circulation anomalies, the warming and enhanced rainfall in the central/east Pacific. Models in group 2 exhibit a westward displacement and/or have weak responses, while group 3 models have the weakest ENSO signatures.