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Clim Dyn (2014) 42:19992018
DOI 10.1007/s00382-013-1783-z
ENSO representation in climate models: from CMIP3 to CMIP5
H. Bellenger E. Guilyardi J. Leloup
M. Lengaigne J. Vialard
Received: 10 December 2012 / Accepted: 22 April 2013 / Published online: 30 April 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract We analyse the ability of CMIP3 and CMIP5 coupled oceanatmosphere general circulation models (CGCMs) to simulate the tropical Pacic mean state and El Nio-Southern Oscillation (ENSO). The CMIP5 multi-model ensemble displays an encouraging 30 % reduction of the pervasive cold bias in the western Pacic, but no quantum leap in ENSO performance compared to CMIP3. CMIP3 and CMIP5 can thus be considered as one large ensemble (CMIP3 ? CMIP5) for multi-model ENSO analysis. The too large diversity in CMIP3 ENSO amplitude is however reduced by a factor of two in CMIP5 and the ENSO life cycle (location of surface temperature anomalies, seasonal phase locking) is modestly improved. Other fundamental ENSO characteristics such as central Pacic precipitation anomalies however remain poorly represented. The sea surface temperature (SST)-latent heat ux feedback is slightly improved in the CMIP5 ensemble but the wind-SST feedback is still underestimated by 2050 % and the shortwave-SST feedbacks remain underestimated by a factor of two. The improvement in ENSO amplitudes might therefore result from error compensations. The ability of CMIP models to simulate the SST-shortwave feedback, a major source of erroneous ENSO in CGCMs, is further detailed. In observations, this feedback is strongly nonlinear because the real atmosphere switches from subsident (positive feedback) to convective (negative feedback) regimes under the effect of seasonal
and interannual variations. Only one-third of CMIP3 ? CMIP5 models reproduce this regime shift, with the other models remaining locked in one of the two regimes. The modelled shortwave feedback nonlinearity increases with ENSO amplitude and the amplitude of this feedback in the spring strongly relates with the models ability to simulate ENSO phase locking. In a nal stage, a subset of metrics is proposed in order to synthesize the ability of each CMIP3 and CMIP5 models to simulate ENSO main characteristics and key atmospheric feedbacks.
1 Introduction
The El Nio-Southern Oscillation (ENSO) is the dominant mode of interannual climate variability. It is characterized by large-scale sea surface temperature (SST) anomalies in the eastern equatorial...