What Controls the Duration of El Niño and La Niña Events?...La Niña Weak El Nino (Jan 1225)...
Transcript of What Controls the Duration of El Niño and La Niña Events?...La Niña Weak El Nino (Jan 1225)...
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What Controls the Duration of El Niño and La Niña Events?
Xian Wu, Yuko Okumura and Pedro DiNezio
University of Texas Institute for Geophysics (UTIG)
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Impact of Multi-year La Nina Events
Contours: SLP (1 hPa)
SST (°C) Precip. (mm/day)
Nov(0)-Apr(1) Nov(1)-Apr(2)
Okumura, DiNezio and Deser (2017, GRL)
Composite Anomalies (HadISST/GPCC/20CR, 1901-2012)
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Diverse Evolution of ENSO EventsNiño-3.4 SST Index
(HadISST, 1900-2016)
El Niño
La Niña
| Niño-3.4 | > 0.75σin Oct(0)-Feb(1)
Dec(0)Dec(-1) Dec(+1)
Dec(0)Dec(-1) Dec(+1)
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What controls the duration of El Niño and La Niña?
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1-yr vs. 2-yr Events: Observations (1900-2016)El
Niñ
oLa
Niñ
a
1-yr Events 2-yr Events
|Niño3.4| < 0.5σin Oct(1)-Feb(2)
|Niño3.4| > 0.5σin Oct(1)-Feb(2)
Composite (p=0.2)
Dec(0)Dec(-1) Dec(+1)
Dec(0)Dec(-1) Dec(+1)
Precedingevent amp.
Onsettiming
Peak amp.
Precedingevent amp.
Peak amp.
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1-yr vs. 2-yr Events: CESM1 PI Control Run (1800 yrs)El
Niñ
oLa
Niñ
a
1-yr Events 2-yr Events
|Niño3.4| < 0.5σin Oct(1)-Feb(2)
|Niño3.4| > 0.5σin Oct(1)-Feb(2)
Composite (p=0.01)
Dec(0)Dec(-1) Dec(+1)
Dec(0)Dec(-1) Dec(+1)
Precedingevent amp.
Onsettiming
Peak amp.
Precedingevent amp.
Peak amp.?
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Relative Importance of These Factors (CESM1)
Precedingevent amp.
Peak amp.
Precedingevent amp.
El Niño
La Niña
Preceding Event Amp. Onset Timing Peak Amp.
Onsettiming
Peak amp.
DiNezio et al. (2017, Clim. Dyn.)
CESM1
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Leading Factors for El Niño and La Niña Duration (CESM1)
OnsetTiming
#%
#%
El Niño La Niña
Niño3.4in Dec(-1)
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How do these factors affect the duration ofEl Niño and La Niña in CESM1?
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Dec(0)
Dec(-1)
Dec(1)
Dec(0)
Dec(-1)
Dec(1)
Dec(0)
Dec(-1)
Dec(1)
Role of Oceanic Adjustments (CESM1)
1-yr Event
Earlier Onset
1-yr minus 2-yr
Apr(1) ZTC
Thermocline Depth (ZTC) and SST Composite Anomalies (3S-3N)
Dec(1) N34r=0.79
Earliernegativefeedback
Apr(1) ZTC
2-yr Event
El N
iño
LaN
iña
Weaker El Nino
Smaller discharge
Dec(-1) N34
r=-0.52
Wind inFeb/Mar(1)
WindFeb/Mar(1)
Dec(1) N34r=0.66
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1-yr
2-yr
Diff(1-2)
SST and Surface Wind Composite Anomalies in Feb/Mar(1) El Niño La Niña
SST (°C)
Role of Atmospheric Adjustments (CESM1)
CAM5 forced with tropical SST anomalies from CESM1 (15 members)
Diff(1-2)
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1-yr Event 1-yr minus 2-yr2-yr EventSST Composite Anomalies (3S-3N)
Interbasin SST AdjustmentsEl
Niñ
oLa
Niñ
a
Indian Pacific Atlantic
SST (°C)
Dec(0)
Dec(-1)
Dec(1)
Earlier onset
Earlierinterbasin
adjustments
Negative SST gradienttoward the Pacific
Dec(0)
Dec(-1)
Dec(1)
WeakerEl Nino
Weakerinterbasin
adjustments
Apr(1)
Apr(1)WeakerLa Nina Positive SST gradient
toward the Pacific
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SummarySummary of Diagnostic Analysis
El Niño
La Niña
Timing of Onset
Timing of1) Thermocline adjustments E Pacific thermocline Duration
2) Indian/Atlantic SST adjustments W Pacific winds
Amplitude of Preceding El Nino
Amplitude of1) Eq. heat content discharge E Pacific thermocline Duration
2) Indian/Atlantic SST adjustments & La Nina W Pacific winds
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Can we predict the duration of El Niño and La Niñaevents based on these factors?
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CESM1 Perfect Model Forecast ExperimentsLa
Niñ
a
Strong El Nino (Jan 1455)Weak El Nino (Jan 1225)30-member ensemble
forecasts initializedwith oceanic conditions
from the CESM1 PIcontrol run
DiNezio et al. (2017, Clim. Dyn.)
Early Onset (Apr 1729) Late Onset (Sep 1236)
El N
iño
20-member ensembleforecasts
What is the predictabilityin the real world?
Analysis of the CESM1decadal prediction
large ensemble(DiNezio et al. 2017, GRL)