Abstract:Observed sea surface temperature anomaly(SSTA) in the equatorial eastern Pacific exhibits an interesting evolution characteristic in La Niña life cycle, which is characterized by a weaker decay after its peak and a re-intensification of cold SSTA in the second year.Based on the output data in 19 CMIP5 models, the special evolution features of La Niña events are investigated.The simulation capability of CMIP5 multi-models for La Niña life cycle is evaluated.Evaluation results show that only a few good models can capture the slow decaying and re-intensification processes in La Niña life cycle, while La Niña continues decaying to the neutral state in the rest of pool models.The physical mechanisms that caused the distinctive evolution features are carried out by an oceanic subsurface heat budget analysis.The result shows that the major differences between good models and pool models lie in wind, which induces anomalous zonal advection and mean meridional advection associated with subtropical cell.The first possible mechanism that caused the re-intensification process of La Niña is the wind-forced equatorial wave dynamics.As both the mean upwelling and the mean zonal temperature gradient along the equator reach a maximum in boreal fall, northern autumn is the season of the strongest coupled ENSO instability when the cold tongue is the strongest.With re-intensification of easterly wind anomalies in northern fall, the thermocline shoals again continue towards the end of the year.Thus, it is found that a positive feedback of SST-convection-wind, which makes La Niña re-develop, can be established in the good models, while such a positive feedback does not exist in the poor models.The other possible mechanism is the meridional mean ocean advection process related to the ocean mean subtropical cell.The good models can simulate the intensity of climatological mean subtropical cell well, thus the off-equatorial anomalous cold subsurface water is likely to be advected equatorward by the mean current, and La Niña intensifies again through the meridional mean ocean advection.In contrast, the pool models are weak in simulating the intensity of mean subtropical cell, therefore the equatorial negative ocean temperature anomaly tends to recover to the neutral state in the end of the second year.