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More Ocean Indices. Paul Knight, Richard Grumm and Paul Roundy PSU Meteorology and NWS State College. Pacific Decadal Oscillation PDA/NPO Oceanic Index. The Pacific Decadal Oscillation ( PDO ) is an index of long-term variability of the sea-surface temperatures of the North Pacific Ocean.

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More ocean indices

More Ocean Indices

Paul Knight, Richard Grumm and Paul Roundy

PSU Meteorology and NWS

State College


Pacific decadal oscillation pda npo oceanic index
Pacific Decadal OscillationPDA/NPO Oceanic Index

  • The Pacific Decadal Oscillation (PDO) is an index of long-term variability of the sea-surface temperatures of the North Pacific Ocean.

    • reflects the dominant mode of SST over the North Pacific Ocean.

    • The PDO can impact the climate.

    • A characteristic that distinguishes the PDO from ENSO is that 20th century PDO events have tended to persist for 20-to-30 years, while ENSO events have typically persisted for 6 to 18 months.

    • also known as the North Pacific Oscillation (NPO) and the terms can be used interchangeably.


Phases of the pdo npo
Phases of the PDO/NPO

  • the high phase of the NPO is the term used to describe a warm PDO and the low phase of the NPO is the term used to describe the cold PDO.

  • Recent research indicates a clear link of the PDO to the ENSO. The Climate Prediction Center thinks that the sign of the PDO may be a composite of a longer term ENSO cycle.



The cold phase
The cold phase

  • Cold PDO regimes prevailed from 1890-1950

    • cold phase index is positive

    • the PDO was higher then average from 1920 to 1950.

    • cold phase may behave like a weak La Nina

      • note colder water in tropical Pacific dominates

      • may enhance impacts of La Nina when they are in phase

    • The cold phase occurs when there is warmer water over the western and central Pacific associated with a deepened Aleutian low.

    • Colder water over eastern and tropical Pacific


The warm phase
The warm phase

  • Warm PDO regimes dominated from 1950 into the 1990’s.

  • During the warm phase, the PDO is negative.

  • On a 30 year time scale, the PDO was lower than average from 1950 to 1980.

  • A negative PDO may act like an El Nino.

  • The warm phase occurs when there is colder water over the western and central Pacific.


The warm phase1
The warm phase

  • Warmer and drier winters in the northern regions of the nation and wetter and cooler winters observed in the southern areas of the United States.

  • El Nino is associated with a negative SOI, weak tropical easterlies and warm Nino3.4 SST’s.


Pdo sst wind vectors mslp anomalies
PDO SST/wind vectors/MSLP anomalies


Pdo enso similarities sst wind vectors mslp anomalies
PDO-ENSO Similarities SST/wind vectors/MSLP anomalies



Pdo summary
PDO Summary

  • Relates to ENSO cycles

    • Frequency of El Nino can be related to PDO phase during the past 30-40 years.

    • PDO can interfere both constructively and destructively with ENSO.

    • PDO may not be independent of ENSO

  • High NPO (warm phase)

    • Cold water in north/central Pacific

    • Warm water along west coast NOAM (fishing industry named phases!)

    • May enhance El Nino effects in eastern US

  • Low NPO (cold phase)

    • Warm water in north/central Pacific

    • La Nina like impact connect with weaker storm tracks, farther north [dry-nation]


Referemces
Referemces

Rogers, J.C., 1997: North Atlantic storm track variability and its association to the North Atlantic Oscillation and climate variability of Northern Europe. Journal of Climate10(7), 1635-1647.

Hurrell, J.W., 1995: Decadal trends in the North Atlantic Oscillation and relationships to regional temperature and precipitation. Science269, 676-679.

Wallace, J.M. and David S. Gutzler, 1981:"Teleconnections in the Geopotential Height Field during the Northern Hemisphere Winter" Mon. Wea. Review,109,784-812.

Teleconnections Linking Wolrdwide Climate Anomalies. ed. M.H. Glantz, R.W. Katz and N. Nicholls, Cambridge University Press, 1991.

Rogers, J.C. and H. Van Loon, 1979: "The Sea-Saw in winter temperatures between Greenland and Northern Europe. Part II. Some atmospheric and oceanic effectes in middle and high latitudes." Mon Wea. Rev. ,107, 509-519.


The large scale convective disturbance
The Large-Scale ConvectiveDisturbance

  • Tropical Intraseasonal or

    Madden-Julian Oscillation


What is the mjo
What is the MJO?

  • Large-scale disturbance of deep convection and winds that controls up to half of the variance of tropical convection in some regions

  • Brief history


Mjo an intraseasonal event
MJO- an intraseasonal event

  • Prior to 1971, it was thought that virtually all variability in the weather conditions within a given season in the Tropics was random.

  • There were indications of interseasonal variations, such as the Southern Oscillation

  • Studies of Tropical rainfall and pressure changes showed additional oscillations


The mjo a description

A 30-60 day oscillation in the coupled Tropical ocean-atmosphere system

An eastward progression of enhanced and suppressed convection

Low level and upper level wind patterns show distinct anomalies

Strong year to year variability in MJO that is related to ENSO cycle

The MJO - A Description


Wave cooperation
Wave Cooperation ocean-atmosphere system

  • Kelvin and Rossby waves linked by convection, land, and air-sea interaction combine to produce the observed disturbance.


Schematic of mature mjo
Schematic of Mature MJO ocean-atmosphere system


The 3d view of mjo
The 3D view of MJO ocean-atmosphere system

  • Axis of coupled convection/suppressed convection usually between 5S-5N

  • SST feedback could be sensitive enough to either trigger or help propagate the wave


Kelvin waves in the ocean
Kelvin Waves in the Ocean ocean-atmosphere system


Convective kelvin wave
Convective Kelvin Wave ocean-atmosphere system

z

Convection removes

Some of the accumulating

mass, slows propagation

H

L

x

Propagation speed: less than 20 ms-1


Mjo statistics
MJO Statistics ocean-atmosphere system

  • Eastward propagation, 4 +/- 2 ms-1. Also has standing wave behavior

  • 30-60 day period

  • Wavenumber 1-4 (planetary scale)

  • Interacts with midlatitudes, but some of this is nonlinear and hard to quantify


Finding the mjo
Finding the MJO ocean-atmosphere system


The satellite view of mjo
The Satellite View of MJO ocean-atmosphere system

  • The MJO is noted by a cluster of thunderstorms drifting eastward along the equatorial Indian and Pacific oceans.


Simplified Madden-Julian Oscillation Composite ocean-atmosphere system

OLR from A.J. Matthews, 2000.


The velocity potential view
The Velocity Potential View ocean-atmosphere system

  • The 200 mb velocity potential illustrates yet another way of detecting both the presence and movement of the MJO. This is noted by a couplet of anomalies.


Disturbances in the 500mb flow
Disturbances in the 500mb Flow ocean-atmosphere system

  • Another method of detecting the presence of the MJO is following height and wind perturbations in the 500 mb flow over the equatorial Pacific ocean.


How does it propagate
How Does It Propagate? ocean-atmosphere system

  • Is a matter of debate, but, probably involves

    • interactions with equatorial waves

      • Kelvin wave

      • Equatorial Rossby wave

    • Feedbacks from convection

    • Sea surface temperatures—air-sea interaction

    • Land interactions


Mjo probable cause
MJO - Probable Cause ocean-atmosphere system

  • Wave-CISK Theory (Chang, Lau, Lim)

    • slow moving wave with conditional instability of the second kind (see Tropical Meteo)

  • Evaporation-wind feedback Theory (Emanuel, Neelin, Wang)

    • diabatic heating due to cumulus convection nearly balanced by adiabatic cooling


Relationship of mjo to north american weather
Relationship of MJO to ocean-atmosphere systemNorth American Weather

  • Most prominent connection to phase of ENSO

  • Winter weather along the West Coast (see figure)

  • Secondary downstream effects in USA

  • Modulation of tropical storm development in Atlantic basin during the summer


The mjo and west coast wx
The MJO and West Coast Wx ocean-atmosphere system


Decay Region ocean-atmosphere system

Formation

Region


Active ocean-atmosphere system

Convection


Enhanced ocean-atmosphere system

Easterlies

Active

Convection


Deflected ocean-atmosphere system

Jet Stream

Active

Convection

Energy Build-up


Cold air outbreak enhancement ocean-atmosphere system

Active

Convection


Mjo a modeler s nightmare

GCM simulation of convection (CPS) ocean-atmosphere system

SST variations not well simulated

Change of phase speed from eastern to western hemispheres

Handling of very low wave number

Recent modifications-

increased vertical resolution

better parameterization of:

radiation

convection

cloud formation

precipitation

surface convergence

MJO - A Modeler’s Nightmare


Prediction of mjo
Prediction of MJO ocean-atmosphere system

  • Global weather models predict it with some skill to about 7 or 8 days

  • Filtering methods allow prediction up to 20 days (Wheeler and Weikmann, 2001)

  • Statistical schemes may allow prediction for more than 40 or 50 day lead times


Mjo research

Chang, Lim, 1988: Kelvin wave-CISK ocean-atmosphere system

Chen, Murakami, 1988: Development and life-cycle of the Indian monsoon

Crum, Dunkerton, 1994: CISK and evaporational-wind feedback

Ferranti, Palmer, Molteni and Klinker,1990: Tropical and extra-tropical interactions associated with 30-60 day oscillation

Gray,1988: Seasonal frequency variations in the 40-50 day cycle

MJO Research


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