ENSIP: the El Nino simulation intercomparison project

M. Latif (1), K. Sperber (2), J. Arblaster (3), P. Braconnot (4), D. Chen (5), A. Colman (6), U. Cubasch (7), C. Cooper (6), P. Delecluse (8), D. Dewitt (9) (), L. Fairhead (10), G. Flato (11), T. Hogan (12), M. Ji (13), M. Kimoto (14), A. Kitoh (15), T. Knutson (16), H. Le Treut (10), T. Li (12), S. Manabe (17), O. Marti (4), C. Mechoso (18), G. Meehl (3), S. Power (19), E. Roeckner (1), J. Sirven (8), L. Terray (20), A. Vintzileos (10), R. Voß (7), B. Wang (21), W. Washington (3), I. Yoshikawa (22), J. Yu (18), S. Zebiak (5)

(1) Max-Planck-Institut für Meteorologie, Hamburg, Germany
(2) Program for Climate Model Diagnosis and Intercomparison, LLNL, Livermore, CA USA
(3) National Center for Atmospheric Research, Boulder, CO, USA
(4) Laboratoire de Modelisation du Climat et de l'Environnement, Saclay, France
(5) Lamont Doherty Earth Observatory, Palisades, NY, USA
(6) UK Meteorological Office, Bracknell, UK
(7) Deutsches Kilmarechenzentrum, Hamburg, Germany
(8) LODYC-IPSL, Paris, France
(9) Center for Ocean-Land-Atmosphere Studies, Calverton, MD, USA
(10) Laboratoire de Meteorologie Dynamique, Paris, France
(11) Canadian Centre for Climate Modelling and Analysis, Victoria, BC, Canada
(12) Naval Research Laboratory, Monterey, CA, USA
(13) National Centers for Environment Prediction, Camp Springs, MD, USA
(14) Center for Climate System Research, Tokyo, Japan
(15) Meteorological Research Institute, Tsukuba, Japan
(16) Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
(17) Earth Frontier Research System, Tokyo, Japan
(18) University of California, Los Angeles, CA, USA
(19) Bureau of Meteorology Research Centre, Melbourne, Australia
(20) CERFACS, Toulouse, France
(21) University of Hawaii, Honolulu, HI, USA
(22) Japan Meteorological Agency, Tokyo, Japan

Abstract An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Nino/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon.