Bor-Ting Jong

Department of Earth and Environmental Sciences, Columbia University, New York, NY

Lamont-Doherty Earth Observatory, Columbia University, Palisade, NY

October 18, 2018

IV International Conference on ENSO

Guayaquil, Ecuador

Mingfang Ting, Richard Seager

• Summer (Jun-Aug): Flowering season for maize & soybean over NA

• Maize and soybean yields are positively correlated with flowering season

Nino3.4 SST anomalies in the US. (Anderson et al. 2017)

(Iizumi et al. 2014)

Impacts of La Niña on crop yields

SoybeanMaize

La Niña life cycle Life cycle of yield anomalies

(Anderson et al. 2017)

1st year La Niña Peak

Transitioning

Maize

Soybean

ON

I

JJA(-1) JJA(0) JJA(1)

Jan(1)Jul(0)Jan(0)Jul(-1) Jul(1)

La Niña life cycle Life cycle of yield anomalies

(Anderson et al. 2017)

Maize

Soybean

Niñ

o3

.4 S

STA

(O

NI)

JJA(-1) JJA(0) JJA(1)

Jan(1)Jul(0)Jan(0)Jul(-1) Jul(1)

JJA(-1) JJA(0) JJA(1)

Physical mechanism that causes this warming?

Ma

xim

um

tem

pe

ratu

re

La Niña life cycle

Niñ

o3

.4 S

STA

(ON

I)

JJA(-1) JJA(0) JJA(1)

Jan(1)Jul(0)Jan(0)Jul(-1) Jul(1)

JJA(-1) JJA(0) JJA(1)

1. The physical process behind the warm anomalies over the Midwest

during ENSO transition summer.

Session5: 10:50 ~ 11:10

How relevant is ENSO to global crop production?

(Weston Anderson)

La Niña life-cycle

La Niñas during 1950-2016

12 8 2

Criteria: ERSSTv5 3-month averaged Nino3.4 SSTA < -0.5ºC

in October-December (OND)

El Niño 1st year La Niña

2nd year La Niña

3rd year La Niña

1st year La Niña

2nd year La Niña

3rd year La Niña

El Niño

Transition Persistent

La Niña life-cycle

Transition Persistent

CRU detrended Ts CRU detrended Ts

JJA(-1) SON(-1) D(-1)JF(0) MAM(0) JJA(0)-t SON(0) D(0)JF(1) MAM(1) JJA(-1) SON(-1) D(-1)JF(0) MAM(0) JJA(0)-p SON(0) D(0)JF(1) MAM(1)

1. The physical process behind the warm anomalies over the Midwest

during ENSO transition summer.

2. The differences between the transition and persistent summers.

Transition Persistent

JJA(-1) SON(-1) D(-1)JF(0) MAM(0) JJA(0)-t SON(0) D(0)JF(1) MAM(1) JJA(-1) SON(-1) D(-1)JF(0) MAM(0) JJA(0)-p SON(0) D(0)JF(1) MAM(1)

D(-1)JF(0)

MAM(0)

JJA(0)

El Niñopeak

La Niña

Tra

nsitio

n

Transition

El Niño La Niña El Niño

NCEP-NCAR R1: detrended SSTA & 200hPa height anomalies (zonal mean removed)

El Niñopeak

La Niña

Tra

nsitio

n

Transition Persistent

La Niñapeak

La Niña

Pe

rsis

ten

t

El Niño La Niña El Niño Only La Niña

NCEP-NCAR R1: detrended SSTA & 200hPa height anomalies (zonal mean removed)

D(-1)JF(0)

MAM(0)

JJA(0)

Transition Persistent

NCEP-NCAR R1: detrended SSTA & 200hPa height anomalies (zonal mean removed)

Teleconnections propagate toward extratropical North America.

Ridge

Anomalous circulations are more confined in the tropics.

0 0

Transition

NCEP-NCAR R1: detrended SSTA & 200hPa height anomalies (zonal mean removed)

Anomalous circulations are more confined in the tropics.

Ridge

00

0

Persistent

Ridge

La NiñaEl Niño

western Pacific:Caused by the delayed Indian Ocean warming due to the previous El Niño.(Xie et al. 2009)

Transition

Ridge

0

0

Ridge

Transition

Ridge

La NiñaEl Niño

H

Convergence

L

0

0

Ridge

Transition

Ridge

La NiñaEl Niño

0

0

0

0

Persistent

Transition Persistent

The suppressed deep convection over the western Pacific due to the previous El Niño also trigger a stationary wave propagate toward NA.

0 0

Stationary wave model (Ting and Hoerling 1993; Ting and Yu 1998)

- Linear, primitive equation, steady-state baroclinic model

- Deviations from a prescribed zonally asymmetric basic state

- Interior Rayleigh drag: 15-day

- Forcing: diabatic heating, transient eddies Transition0

Stationary wave model (Ting and Hoerling 1993; Ting and Yu 1998)

- Linear, primitive equation, steady-state baroclinic model

- Deviations from a prescribed zonally asymmetric basic state

- Interior Rayleigh drag: 15-day

- Forcing: diabatic heating, transient eddies

El Niño winter : NCEP-NCAR reanalysis Model output

Contour: stream functionShaded: diabatic heating (prescribed)

Transition JJA(0)Diabatic heating anomalies @ 400hPa

Central tropical Pacific (CP)

Western tropical Pacific (WP)

Western & Central tropical Pacific(WP+CP)

Shaded: 200hPa streamline function anomalies

Observation

WP+CP

Model

0

Shaded: 200hPa streamline function anomalies

Observation

WP+CP

Model

0

Shaded: 200hPa streamline function anomalies

CP WP

WP+CP

Model

0

Observation

Observation Model

Transition

Persistent

Diabatic heating

0

0JJA(0)

JJA(0)

Shaded: 200hPa streamline function anomalies

Shaded: 200hPa streamline function anomalies

Observation Model

Transition

Persistent

CP

WP+CP

Transition Summer Q

Transition

Persistent

0

0

Observation Forcing: Q

Transition

Persistent

0

0

Shaded: 200hPa streamline function anomalies

Observation

Transition

Persistent

Forcing: Q Forcing: Q + Transient eddiesRidge

Ridge

Transition

Persistent

0

0

Shaded: 200hPa streamline function anomalies

Transition

Persistent

Forcing: Q Forcing: Q + Transient eddies

Transition

Persistent

Shaded: 200hPa streamline function anomalies

Transition

Persistent

Forcing: Q Forcing: Q + Transient eddies

Transition

Persistent

Shaded: 200hPa streamline function anomalies

Persistent

Different tropical forcing

Transition

Different anomalous circulation

Differenttransient eddies

response

Differentfeedback to

teleconnections

Forcing: Q Forcing: Q + Transient eddiesDiabatic heating

• Robust warm anomalies over the Midwest

during transition summer (El Niño -> La Niña)

• During transition summer, two suppressed deep convections:

- central tropical Pacific (developing La Niña)

- western tropical Pacific (decaying El Niño)

• According to SWM experiments,

- Diabatic cooling over WP: shift the teleconnections

- Transient eddies: shape the details of teleconnections over the extratropics

Transition

0

Rossby waves from both forcings

0