Precursors of ENSO Diversity in the NCAR CESM2 Climate Model

Considerable progress has been made over the last two decades in understanding ENSO diversity, including spatial pattern, magnitude, and temporal evolution. However, open questions remain concerning the relative role of different precursors in triggering different types of ENSO events. These precursors include Warm Water Volume and Westerly Wind Burst activity in the equatorial Pacific, as well as extra-tropical influences, in the form, e.g., of the North and South Pacific Meridional Modes. In this presentation, we revisit these issues in the context of a 1000-year pre-industrial simulation performed with the recently released NCAR-CESM2 climate model. Using different ENSO diversity metrics, we first assess the representation of ENSO diversity in the model. We then use a Linear Inverse Modeling approach to objectively determine the precursors of different ENSO types, and examine the temporal evolution of these different ENSO flavors from the precursor stage to the mature event stage. Mechanisms responsible for the decadal modulation of ENSO diversity in the model are also discussed.