Reasonable ENSO simulaiton skill in coupled models is one of the premise of improving the ENSO prediction skill with dynamical models. The current coupled models are still struggling with the simulation of ENSO period, although they can accuartly simulate other ENSO behaviors to some extent. Here we have investigated the root causes for ENSO period simulation biases in the current coupled models. By decomposing the relevant air-sea feedback processes responsible for the ENSO discharge-recharge framwork, we have revealed that the different ENSO period in the coupled models primarily arises from the different thermocline change rates in response to a unit wind stress curl anomaly, which is in association with the corresponding precipiation anomaly response pattern. Such air-sea feedback biases on the interannual time scale can be further attributed to the background mean state biases. Through conducing several suits of sensitivity experiments, we have shown the physical factors responsible for ENSO period simulation bias in coupled models.
 

ENSO period, Physical process-oriented analysis, ENSO meridional structure