ENSO dynamics in the GFDL SPEAR_LO climate model

Abstract:

We assess the dynamics of the El Niño / Southern Oscillation (ENSO) as simulated in the SPEAR_LO global coupled GCM, recently developed by NOAA's Geophysical Fluid Dynamics Laboratory (GFDL). SPEAR_LO supports seasonal-to-centennial climate research, forecasts, and projections, and contributes routine seasonal forecasts as part of the North American Multi-Model Ensemble (NMME). Compared to its predecessors, SPEAR_LO simulates improved ENSO patterns, spectra, seasonal timing, teleconnections, and ocean-atmosphere feedbacks. Analyses of the upper-ocean heat budget and ocean-atmosphere feedbacks illustrate how SPEAR's improved physical formulations contribute to more realistic simulations of the tropical Pacific climatology and ENSO. Further correcting the tropical climatology — via flux-adjustments of the model SST, SSS, and surface wind stress — yields an even better simulation of ENSO, and illuminates the roles of the background state in ENSO dynamics and feedbacks. Promising avenues toward future model improvements are discussed, along with implications for the Tropical Pacific Observing System (TPOS) and community-developed metrics to assess ENSO in climate models.