Teleconnections and the MJO: intraseasonal and interannual

variability

Steven Feldstein

June 25, 2012 University of Hawaii

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.

• 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)

Pow

er

Period (years)

Pow

er

POWER SPECTRA

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

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

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

Physical processes for the PNA

In contrast to the NAO, the PNA is dominated bylinear processes: stationary eddy advection.

• Both phases of the PNA are excited by tropical convection

Tropical convection excites a small amplitude Rossby wave train via linear dispersion

Synoptic-scale eddies (remote pos phase; local neg phase) amplify PNA

OLR anomalies associated with the PNA

300-hPa streamfunction anomalies associated with OLR

PAPNA PNA

PNA Life Cycle

Summary of Physical Processes

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

•Interannual variability of most teleconnection patterns arises primarily from climate noise

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

• The PNA wavetrain is excited by tropical convection and then amplified by breaking synoptic-scale waves; primarily a linear process

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)

Does the MJO affect Arctic surface air temperature?

MJO Phase 1 (neg PNA) MJO Phase 5 (pos PNA)

Zonal-mean zonal wind and temperature

MJO Phase 1 (neg PNA) MJO Phase 5 (pos PNA)

Eliassen-Palm Fluxes associated with the MJO

MJO Phase 1 (Phase 5) associated with a reduced (increased) poleward heat and wave activity flux

Planetary-scale (k-1,3)

Synoptic-scale (k=4,8)

Summary of physical processes (projections onto 7-10 day SAT)

MJO Phase 5 (pos PNA)MJO Phase 1 (neg PNA)

Mean Meridional Circulation

Negative PNA Positive PNA

Multi-level primitive equation model calculation of MJO-induced Arctic SAT change (GFDL dynamical core)Use MJO-like steady heating profiles for MJO phases 1 and 5 (100 randomly selected ensemble members): Initial value problem

MJO

phase

1

MJO

phase

5

MJO-induced poleward tracer (H20) transportComposite evolution of anomalous tracer concentration

MJO

phase

1

MJO

phase

5

Tracer (H20) transported equatorward (poleward) duringMJO phase 1 (phase 5) (Perhaps can explain observed downward IRassociated with MJO)

Sensitivity of midlatitude response to initial conditions

Projections onto 7-13 day SAT

Response to MJO convection very sensitive tointial conditions

MJO Phase 1 (neg PNA) MJO Phase 5 (pos PNA)

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 and arises from synoptic-scale wave breaking and the PNA as a Rossby wave train response to MJO convection followed by amplification by synoptic-scale wave breaking

•MJO impacts Arctic SAT through changes in the excitation of poleward Rossby wave propagation (poleward heat flux and eddy-induced adiabatic warming/cooling) : Poleward Rossby wave propagation is weakened (strengthened) in MJO phase 1 (phase 5) and is associated with less (more) localized tropical convection

•Downward IR (surface sensible and latent heat flux) enhances (weakens) the impact of the MJO on Arctic SAT

•Anomalous downward IR may be associated with changes in poleward moisture transport associated with MJO