Simulations of ENSO Phase-locking in CMIP5 and CMIP6

Journal Article · Wed Mar 24 00:00:00 EDT 2021 · Journal of Climate

DOI:https://doi.org/10.1175/jcli-d-20-0874.1· OSTI ID:1850896

Chen, Han-Ching ^[1]; Jin, Fei-Fei ^[2]

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1. Univ. of Hawaii at Manoa, Honolulu, HI (United States). Dept. of Atmospheric Sciences; Univ. of Hawaii at Manoa, Honolulu, HI (United States)
2. Univ. of Hawaii at Manoa, Honolulu, HI (United States). Dept. of Atmospheric Sciences

The characteristics of El-Niño-Southern Oscillation (ENSO) phase-locking in observations and CMIP5 and CMIP6 models are examined in this study. Two metrics based on the peaking month histogram for all El Niño and La Niña events are adopted to delineate the basic features of ENSO phase-locking in terms of the preferred calendar month and strength of this preference. It turns out that most models are poor at simulating the ENSO phase-locking, either showing little peak strengths or peaking at the wrong seasons. By deriving ENSO’s linear dynamics based on the conceptual recharge oscillator (RO) framework through the seasonal linear inverse model (sLIM) approach, various simulated phase-locking behaviors of CMIP models are systematically investigated in comparison with observations. In observations, phase-locking is mainly attributed to the seasonal modulation of ENSO’s SST growth rate. In contrast, in a significant portion of CMIP models, phase-locking is co-determined by the seasonal modulations of both SST growth and phase-transition rates. Further study of the joint effects of SST growth and phase-transition rates suggests that for simulating realistic winter peak ENSO phase-locking with the right dynamics, climate models need to have four key factors in the right combination: (1) correct phase of SST growth rate modulation peaking at the fall; (2) large enough amplitude for the annual cycle in growth rate; (3) amplitude of semi-annual cycle in growth rate needs to be small; and (4) amplitude of seasonal modulation in SST phase-transition rate needs to be small.

• Research Organization: Univ. of Hawaii, Honolulu, HI (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC)
• Grant/Contract Number: SC0005110
• OSTI ID: 1850896
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 12 Vol. 34; ISSN 0894-8755
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
Climate models
Dynamics
ENSO
Interannual variability
Meteorology & Atmospheric Sciences
Sea surface temperature
Seasonal cycle
Thermocline