A Coupled Dynamic Index for ENSO Periodicity

El Niño–Southern Oscillation (ENSO) is the most active interannual climatic mode, with great global impacts. The state-of-the-art climate models can simulate this dominant mode variability to a large extent. Nevertheless, some of ENSO’s fundamental time–space characteristics still have a large sprea...

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Vydáno v:Journal of climate Ročník 31; číslo 6; s. 2361 - 2376
Hlavní autoři: Lu, Bo, Jin, Fei-Fei, Ren, Hong-Li
Médium: Journal Article
Jazyk:angličtina
Vydáno: Boston American Meteorological Society 15.03.2018
Témata:
Anomalies
Atmospheric sciences
Climate
Climate models
Computer simulation
Dynamic stability
Dynamics
El Nino
El Nino phenomena
El Nino-Southern Oscillation event
Enthalpy
Frameworks
Heat
Heat content
Instability
Intercomparison
Laboratories
Ocean-atmosphere interaction
Oceanic analysis
Periodicity
Recharging
Southern Oscillation
Thermocline
Wind stress
Beijing China
China
ISSN:0894-8755, 1520-0442
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Shrnutí:El Niño–Southern Oscillation (ENSO) is the most active interannual climatic mode, with great global impacts. The state-of-the-art climate models can simulate this dominant mode variability to a large extent. Nevertheless, some of ENSO’s fundamental time–space characteristics still have a large spread in the simulations across the array of recent climate models. For example, the large biases of ENSO periodicity still exist among model simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Based on the recharge oscillator framework, a coupled dynamic index for ENSO periodicity is proposed in this study, referred to as the Wyrtki index, in parallel to the Bjerknes index for ENSO instability. The Wyrtki index provides an approximate dynamic measure for ENSO linear periodicity. It has two main contribution terms: the thermocline and zonal advective feedbacks (or F factor) multiplied by the efficiency factor B of discharging–recharging of the equatorial heat content driven by ENSO wind stress anomalies. It is demonstrated that the diversity of simulated ENSO periodicity in CMIP5 models results from the biases in mean state and several key parameters that control ENSO dynamics. A larger F factor would result in a shorter ENSO period [e.g., BCC_CSM1.1(m)], whereas a smaller B factor would lead to a longer ENSO period (e.g., HadGEM2-ES). The Wyrtki index serves as a useful tool for a quantitative assessment of the sources for ENSO periodicity in reanalysis data and its biases in CMIP5 model simulations.
Bibliografie:ObjectType-Article-1
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ISSN:0894-8755
1520-0442
DOI:10.1175/jcli-d-17-0466.1