Exploration on Dynamics of El Niño Diversity Based on Nonlinear Forcing Singular Vector‐Assimilation Approach

Climate models still encounter challenges in simulating the El Niño diversity, namely the central Pacific (CP) and eastern Pacific (EP) El Niño. This limitation restricts the climate study and prediction. The present study employs the nonlinear forcing singular vector (NFSV)‐assimilation method to optimize an intermediate coupled climate model (ICM). With the NFSV‐assimilation, two types of optimized forcing vectors (OFVs) corresponding to CP and EP El Niño are derived: CP‐OFV and EP‐OFV. These vectors representing unresolved mechanisms related to El Niño types are used to drive the ICM, thereby constructing CP‐ICM and EP‐ICM. The CP‐ and EP‐ICMs can effectively characterize the evolutions and air‐sea coupling processes of CP and EP El Niño, respectively. Further, based on the CP‐ICM, sensitivity experiments are devised to explore the impacts of the wind forcing and thermocline on the CP El Niño simulations. Both the intensification of the wind forcing and thermocline effects warm the CP but the former tends to cool the EP from the sensitivity experiments. The distinct effect in the EP is attributed to the meridional advection. For the CP, the underlying mechanisms also vary. The CP warming is mainly attributed to the zonal advection feedback in the wind‐dominated climate system whereas the thermocline feedback also serves as a crucial oceanic process in the thermocline‐dominated climate system. This research not only deepens the understanding of the dynamic of the CP El Niño but also provides an effective model platform for further studying the El Niño diversity.