ENSO Dynamics in the E3SM-1-0, CESM2, and GFDL-CM4 Climate Models

Journal Article · Mon Nov 01 00:00:00 EDT 2021 · Journal of Climate

DOI:https://doi.org/10.1175/jcli-d-21-0355.1· OSTI ID:1860738

Chen, Han-Ching ^[1]; Jin, Fei-Fei ^[1]; Zhao, Sen ^[2]; Wittenberg, Andrew T. ^[3]; Xie, Shaocheng ^[4]

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1. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
2. Univ. of Hawaii at Manoa, Honolulu, HI (United States); Nanjing Univ. of Information Science and Technology (China)
3. National Oceanic and Atmospheric Administration (NOAA), Princeton, NJ (United States)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

We report that this study examines historical simulations of ENSO in the E3SM-1-0, CESM2, and GFDL-CM4 climate models, provided by three leading U.S. modeling centers as part of the Coupled Model Intercomparison Project phase 6 (CMIP6). These new models have made substantial progress in simulating ENSO’s key features, including: amplitude; timescale; spatial patterns; phase-locking; spring persistence barrier; and recharge oscillator dynamics. However, some important features of ENSO are still a challenge to simulate. In the central and eastern equatorial Pacific, the models’ weaker-than-observed subsurface zonal current anomalies and zonal temperature gradient anomalies serve to weaken the nonlinear zonal advection of subsurface temperatures, leading to insufficient warm/cold asymmetry of ENSO’s sea surface temperature anomalies (SSTA). In the western equatorial Pacific, the models’ excessive simulated zonal SST gradients amplify their zonal temperature advection, causing their SSTA to extend farther west than observed. The models underestimate both ENSO’s positive dynamic feedbacks (due to insufficient zonal wind stress responses to SSTA) and its thermodynamic damping (due to insufficient convective cloud shading of eastern Pacific SSTA during warm events); compensation between these biases leads to realistic linear growth rates for ENSO, but for somewhat unrealistic reasons. The models also exhibit stronger-than-observed feedbacks onto eastern equatorial Pacific SSTAs from thermocline depth anomalies, which accelerates the transitions between events and shortens the simulated ENSO period relative to observations. Implications for diagnosing and simulating ENSO in climate models are discussed.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); National Oceanic and Atmospheric Administration (NOAA), Princeton, NJ (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC52-07NA27344; SC0005110
• OSTI ID: 1860738
• Report Number(s): LLNL-JRNL-822950; 1035575
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 23 Vol. 34; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES