ENSO diversity in climate models within the recharge oscillator framework

This study is focused on analysing the phase space dynamics of the El Niño-Southern Oscillation (ENSO) for two different types of ENSO, Eastern Pacific ( EP ) and Central Pacific ( CP ) against the thermocline depth ( h ) in the Coupled Model Intercomparison Projects (CMIP) 5 and 6 model simulations. We find that the CMIP models are capable of simulating the different dynamics between EP and CP variability, with weaker interaction between CP and h as compared to EP and h , suggesting that EP is more dynamically coupled to h than CP , as it is observed. CMIP models reproduce the faster phase transition speed for EP , whereas, for CP , they replicate the weaker or slower observed phase transitions. However, CMIP model ensembles have substantial limitations and reproduce most observed characteristics with much weaker intensities, resulting into ENSO variability that is less diverse in the large-scale variability than observed. We further find that the interactions with the thermocline depth is dynamically shifted to the east, which is in particular affecting the interactions for CP dynamics. There is also a large spread within the model ensemble, with only a few CMIP models accurately simulating the observed asymmetry of the ENSO phase space for EP and CP . Further, we found no significant improvement from CMIP 5 to CMIP 6 models in simulating the observed phase space dynamics of ENSO diversity.