Teleconnections: physical processes and applications

Steven Feldstein

April 2, 2009 Climate Prediction Center

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Climate Prediction Center

The dominant Northern Hemisphere teleconnection patterns

North Atlantic Oscillation Pacific/North American pattern

NORTH ATLANTIC OSCILLATION

University of Hamburg

Earliest NAO observations

Norse (Viking) settlers arrived in Greenland in CE 985. The Norse, who appeared to be very interested observers of the weather, also seemed to be aware of teleconnection patterns in the North Atlantic basin.

There was an anonymous Norwegian book (approx. CE 1230), entitled the `King's Mirror'. This book, in the form of a discussion between father and son, wrote that severe weather in Greenland coincides with warmer weather at distant locations, and vice versa.

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• Danish missionary Hans Egede (1745) wrote:

“In Greenland, all winters are severe, yet they are not alike. The Danes have noticed that when the winter in Denmark was severe, as we perceive it, the winter in Greenland in its manner was mild, and conversely.”

Hans Egede map in “History of Greenland”

• Walker (1932) used correlation analysis to find the dominant teleconnection patterns, including the NAO.

SEASONAL ROTATED EOFS

DAILY ROTATED EOFS

seasonal NAO

daily NAO

seasonal PNA

daily PNA

Feldstein (2000)

Corr=0.98 Corr=0.97

NAO PNA

Period (years)

€

100

€

10−1

€

10−2

€

10−3

€

101

Pow

er

Period (years)

€

100

€

10−1

€

10−2

€

10−3

€

101

Pow

er

€

x t = αx t−1 + Ft

POWER SPECTRA

€

f (ω) =σ x

2(1−α 2)

π (1− 2α cosω +α 2)

An AR(1) process

Power spectral density function

Feldstein (2000)

= 9.5 days = 7.7 days

DAILY NAO INDEX & FORECAST (since ~2002)

Climate Prediction Center

Implication for interannual variability?

Feldstein (2002)

Climate Noise: relationship between daily &interannual NAO variability

Feldstein (2002)

Most interannual NAO variability is from Climate Noise€

Snao2 /SAR(1)

2 =1.09

Physical processes of the NAO

Projections

Streamfunction tendency equation

NAO

Feldstein (2003)

NAO AMPLITUDE

Nonlinear

Linear

High-frequency eddies

Low-frequency eddies

Divergence

Vorticity Advection

€

∂ψ /∂t = Linear Nonlinear+

NAO DRIVING MECHANISMS

Feldstein (2003)

Benedict et al. (2004)

Day 1

Day 4

Day 7

Day 10

MODEL SIMULATIONNAO -NAO +

Franzke et al. (2004)

Init

ial p

ertu

rbat

ion

Area of small potential vorticity gradient

Summary of Physical Processes

• Prominent Northern Hemisphere teleconnection patterns have a timescale of 7-10 days

• Interannual variability of most teleconnection patterns arises from climate noise, not necessarily from SST and/or sea ice

• The NAO is comprised of the remnants of breaking synoptic-scale waves; nonlinear process

• The PNA is primarily a linear dynamical process

Investigation of North Pacific Investigation of North Pacific Variability (Continuum Variability (Continuum

Perspective)Perspective) Describe the continuum of North Pacific SLP patterns based on daily,

wintertime SLP data (1958-2005)

Investigate intraseasonal (MJO) and interannual (ENSO) variability of North Pacific SLP field from continuum perspective

Describe intraseasonal and interannual temporal changes in the frequency distribution of North Pacific SLP patterns in connection with the MJO and ENSO

Tropical Convection Associated with Tropical Convection Associated with the Madden-Julian Oscillation (MJO)the Madden-Julian Oscillation (MJO)

Phase 1

Phase 2

Phase 3Phase 4

Phase 5

Phase 6

Phase 7

Phase 8

Time between Phases ~ 6 days

180 ۫° 60 ۫°W20 ۫°E

Dominant intraseaonal oscillation in the tropics

MJO cycle: 30-60 days

Shading OLR

Time between phases ~ 6 days

From Wheeler and Hendon (2004)

From Wheeler and Hendon (2004)

Continuum of North Pacific SLP PatternsContinuum of North Pacific SLP Patterns

Timescale of each pattern ~ 5-10 days

Lower Numbers:

- Low Pressure

- Positive PNA

Higher Numbers:

- High Pressure

- Negative PNA

123456789101112131415161718192021222324

Timescale of each pattern ~ 5-10 days

Timescale of each pattern ~ 5-10 days

Timescale of each pattern ~ 5-10 days

Relationship between North Pacific SLP Relationship between North Pacific SLP Patterns and the MJOPatterns and the MJO

Phase 1

Pattern 23 Pattern 24-100: No occurrence

0: Same frequency of occurrence as average

100: Twice as frequent as average

200: Three times as frequent as average

Number of days after the onset of the MJO Phase

Phase 2Phase 3Phase 4

Pattern 2

Phase 5

120°E

Phase 6Phase 7Phase 8

120E

Black: Significant above 99% Confidence Level

Gray: Significant above 95% Confidence Level

Pattern Number

All WinterMonths

La Niña Neutral ENSO El Niño

1 3.7 0.8 2.6 7.92 4.0 3.1 4.1 4.63 3.4 3.0 3.5 3.44 4.8 5.2 3.9 5.85 6.0 4.9 5.5 7.76 4.0 4.3 4.4 2.97 4.3 1.6 4.4 6.58 3.9 3.2 3.3 5.59 4.4 4.6 3.7 5.5

10 4.5 4.3 4.0 5.611 5.2 5.7 5.7 4.012 5.5 3.6 6.5 5.7

13 4.3 3.7 5.0 3.714 3.1 3.2 3.7 2.015 4.1 4.2 4.5 3.516 4.2 5.1 4.6 2.717 4.9 5.7 4.3 5.218 3.8 3.8 4.6 2.519 4.1 6.1 4.4 2.020 4.1 6.5 3.7 2.621 4.0 6.1 3.3 3.3

22 3.8 5.0 4.0 2.623 2.6 1.8 3.1 2.424 3.2 4.6 2.9 2.6

Relationship between North Pacific SLP Patterns and Relationship between North Pacific SLP Patterns and ENSO: Frequency of ENSO: Frequency of Occurrence (%) during La Niña, Neutral ENSO, and El Niño MonthsOccurrence (%) during La Niña, Neutral ENSO, and El Niño Months

Implications of the Tropical OLR/North Pacific SLP Implications of the Tropical OLR/North Pacific SLP

RelationshipsRelationships Tropical convection associated with both the MJO

and ENSO excites the PNA pattern.

The MJO and ENSO, however, excite different members of the PNA continuum.

North Pacific SLP field may be predictable 2 to 3 weeks in advance.

APPLICATION: Middle Eastern precipitation

Is Middle East precipitation associated with the variability of a particular teleconnection pattern?

Data and methodology

Data: daily precipitation data averaged over 12 sites in Israel. (Ziv et al. 2006, Quart. J. Roy. Meteorl. Soc.)

Calculate composite 300-hPa geopotential height field for dates with extreme precipitation

Daily SL (Southern Levant) index obtained by projecting the daily 300-hPa geopotential height field onto composite pattern

Feldstein and Dayan (2008)

Middle Eastern precipitation

Composite 300-hPa geopotential height field:Southern Levant (SL) pattern

H

L

Middle Eastern precipitation

Feldstein and Dayan (2008)

300-hPa geopotential evolution - Middle Eastern precipitation

Feldstein and Dayan (2008)

-6 days -4 days -2 days

0 days +2 days +4 days

+5 days +7days +9 days

Wave Packet & Middle East precip

Wave packet first observed in the northeast Pacific. The packet travels 3/4 of the distance around the earth before decaying over the northwest Pacific

Wave packet amplifies as it passes over western Europe and the Middle East. This coincides with enhanced precipitation over the Israel.

The wave packets have an eastward group velocity with a near zero phase velocity.

Are these wave packets related to the circumglobal teleconnection pattern (Branstator 2002)?

Circumglobal Teleconnection Pattern

Time-averaged

V over

persistent event

(lag -6 to lag +9 days)

Correlation with EOF1 =0.83 Correlation with EOF1 =-0.72

Wave packets associated with SL precip

300

wet dry

EOF1

Feldstein and Dayan (2008)

-6 days -4 days -2 days

0 days +2 days +4 days

+5 days +7days +9 days

Wave packet evolution & potential vorticity gradient

Some Implications

• The circumglobal wave packet may be a fundamental pattern of variability.

• The circumglobal wave packet can influence interannual Middle East precipitation through climate noise.

• Global warming --> poleward movement of extratropical wave guide (rising of tropopause) --> circumglobal wave packets move north of the Middle East --> disappearance of Jordan and Euphrates Rivers (Kitoh et al. 2008)

• Forecasting: circumglobal wave packets used for 7-day forecast of rain-gauge level precipitation with a hidden Markov model (Samuels, Lall, and Feldstein 2008) (water resources planning)

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Precipitation change: ave(2080-2099) - ave(1980-1999)

IPCC 2007

Concluding remarks

• Most of the major teleconnection patterns have a time scale of less than 10 days

• Most of the interannual variability of the major teleconnection patterns arises from climate noise

• The NAO arises from nonlinear processes (wave breaking), while the PNA arises from linear processes

• North Pacific and North Atlantic variability can be understood in terms of a continuum of teleconnection patterns

•The circumglobal wave packet excites Middle East precipitation

•Global warming: poleward movement of extratropical wave guide --> circumglobal wave packets bypass the Middle East.

Middle East Precipitation

• Precipitation occurs when a circumglobal wave packet passes over western Europe & the Middle East

• The wave packet is initiated over the northeast Pacific, travels eastward, until it decays over the northwest Pacific;

group velocity: about 25 degrees longitude/day phase velocity: close to zero

•Interannual variability of Middle East precip (droughts and floods) is associated with the winter-mean phase of wave packet.

• Much of the interannual Middle East precip variability is due to climate noise

•The circumglobal teleconnection pattern can be understood as a time average of the circumglobal wave packet confined to subtropical & extratropical wave guides (jets): a fundamental pattern

• Global warming: poleward movement of extratropical wave guide (rising of tropopause) circumglobal wave packets bypass the Middle East.

Nonlinear eddy fluxes

Vorticity advection

Planetary vorticity advection

Relative vorticity advection

EA/WR streamfunction tendency equation

LHS of streamfunction tend. equation

RHS of streamfunction tend. equation

Vorticity advection + nonlinear eddy fluxes

Divergence

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Circumglobal Teleconnection Pattern (Branstator 2002)

-remote ENSO response-global change experiments

From from NCAR Community Climate Model

1 9 6 0 1 9 6 5 1 9 7 0 1 9 7 5 1 9 8 0 1 9 8 5 1 9 9 0 1 9 9 5

0

2 0 0

4 0 0

6 0 0

8 0 0

1 0 0 0

T i m e ( m o n t h )

P

r

e

c

i

p

.

a

m

o

u

n

t

(

i

n

/

m

o

n

t

h

)

9 5 % U n c . 5 0 % U n c . O b s e r v e d P r e d i c t e d

7-day Precipitation forecast using nonhomogeneous hidden Markov model external parameter: circumglobal wave packet

Samuels, Lall, Feldstein (2008)

Are the previous solutions robust?

NAO + (35 model runs)

NAO - (35 model runs)

Franzke et al. (2004)

low-lat initial perturbation

high-lat initial perturbation

mid-lat initial perturbation

Are teleconnection patterns characterized by

1. a small number of recurrent regimes (NAO, PNA, etc.): enhanced

predictabilityor

2. a continuum of patterns (NAO- and PNA-like patterns): reduced predictability

Regimes vs. Continuum

Franzke and Feldstein (2005)

1s, t ( ) ( )

Mm m

ma t e s

=ψ( ) = ⋅∑

• Teleconnections become non-orthogonal BASIS FUNCTIONS

( )ma t

: teleconnection patterns (e.g., NAO, PNA spatial patterns)( )me s

: amplitude time series (e.g., NAO, PNA indices)

Regimes vs. Continuum

• Define teleconnections as a sequence of one-point regression patterns

Franzke and Feldstein (2005)

Joint Probability Density Functions

Teleconnections form a continuum

WP

NA

O

EA

PN

A

Franzke and Feldstein (2005)