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On the robustness of the evaluation of ENSO in climate models: How many ensemble members are needed?

Presentation Date
Friday, December 17, 2021 at 8:40am
Location
Convention Center - Room 280-282
Authors

Author

Abstract

Large ensembles of model simulations require considerable resources, and thus defining an appropriate ensemble size for a particular application is an important experimental design criterion. We estimate the ensemble size (N) needed to assess a model's ability to capture observed El Niño-Southern Oscillation (ENSO) behavior by utilizing the recently developed CLIVAR ENSO Metrics Package (Planton et al., 2021, BAMS). Using the larger ensembles available from CMIP6 and the Single-Model Initial condition Large Ensembles (SMILEs) Project, we find that larger ensembles are needed to robustly capture baseline ENSO characteristics (N > 65) and physical processes (N > 50) than the background climatology (N ≥ 12) and remote ENSO teleconnections (N ≥ 6). While these results vary somewhat across metrics and models, our study highlights that ensembles are required to robustly evaluate simulated historical ENSO behavior, and provide initial guidance for designing model ensembles to reliably evaluate and compare ENSO simulations.

Funding Program Area(s)