On the Slow Decay of El Niño in CMIP6 Models

Abstract The decay pace of El Niño can significantly modify its impacts on the Asian climate during the post‐El Niño summer. Hence, accurately reproducing the observed decay pace in state‐of‐art coupled models is essential for realistic climate simulations. In the Coupled Model Intercomparison Project models, El Niño decays slower than observed. This slower decay can be attributed to weaker‐than‐observed air‐sea coupling in the models that causes a weaker atmospheric convective response and smaller westerly anomalies along the equatorial Pacific during the El Niño life cycle. The smaller westerly anomalies result in a slower discharge of equatorial ocean heat, weaker negative/positive thermocline anomalies along/off the equator and thus a weaker meridional gradient of the thermocline anomalies. This weakens the easterly current anomalies, diminishes the zonal advection feedback, and ultimately slows the decay pace of El Niño in the models.