Variations in the Activity of the Variations in the Activity of the

Madden-Julian Oscillation:Madden-Julian Oscillation:

Implications for the Southern HemisphereImplications for the Southern Hemisphere

Charles JonesCharles Jones

University of CaliforniaUniversity of California

Santa BarbaraSanta Barbara

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Collaboration: Leila Carvalho (USP)

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Outline

Brief overview of the MJO

Example of importance of the MJO for the midlatitudes of the southern hemisphere

Outstanding issues about the MJO

1958-2006

The Madden-Julian Oscillation

Power spectrum of zonal winds at 850-hPa

o Originally discovered in early 1970’so Most important mode of tropical

intraseasonal variations o Time scales of 30 to 60 dayso Anomalies propagate eastward

along the tropical belt; phase speeds ~ 5 m s-1

o Eastern hemisphere: strong interaction with clouds, rain, surface winds and large-scale circulationo Western hemisphere: modest

interaction with convection and large-scale circulationo Significant case-to-case and

interannual variability

30-60 days

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Modulate the variability of the monsoons in Asia-Australia, Africa and Americas

Teleconnections with extratropics in both hemispheres

Modulate thermocline variability in the tropical Pacific Ocean via westerly wind bursts; interaction with El Niño/Southern Oscillation (ENSO)

Influence on forecast skills in the tropics and extratropics

Major MJO Climate Influences

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Madden-Julian Oscillation (MJO) Life CycleMadden-Julian Oscillation (MJO) Life Cycle

Eastward propagation of enhanced Convection

Tim

e

-15 Days

-5 Days

5 Days

15 Days

Hendon and Salby (1994)

Anomalous upper level circulation (200-hPa)

Enhanced Convection in the western Pacific

Coupled Forced Rossby-Kelvin wave response

Rossby waves

-+ -

+

Midlatitude wave train

Kelvin wave

Madden-Julian Oscillation (MJO) Life CycleMadden-Julian Oscillation (MJO) Life Cycle

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Antarctic Oscillation (AAO) or Southern Annular Mode (SAM)

Antarctic Oscillation (AAO) or Southern Annular Mode (SAM)

One of the most important modes of weather and climate variability in the high latitudes of the

southern hemisphere

One of the most important modes of weather and climate variability in the high latitudes of the

southern hemisphere

Carvalho et al. (2005): Opposites phases of the Antarctic Oscillation and relationships with intraseasonal-to-interannual activity in the tropics during austral summer. J. Climate

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Objective

Identify variations in extratropical cyclones properties during distinct phases of the Antarctic Oscillation

Murray and Simmons (1991) tracking scheme was applied to track storms with origin south of 50oS during summer (DJF) 1979-2000.

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The Daily AAO Index1979-2000

• The daily AAO index: leading mode of the EOF analysis of daily anomalies of 700hPa geopotential height (H700) from Reanalysis (20-90 S).

• Positive (negative)

phases of the AAO : time coefficient of the

first EOF is greater (less) than 1 standard deviation of the DJF time series.

POSITIVE PHASE

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Extratropical Cyclones properties – Obtained from tracking scheme based on Murray and Simmonds (1991)

Carvalho et al. 2005

Minimum PressureMaximum latitude

Life cycle duration * 12 h

AAO-AAO- AAO-AAO-

AAO-AAO-

AAO+AAO+ AAO+AAO+

AAO+AAO+

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What are the relationships between the MJO and AAO?

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Lag composites (Days) OLR anomalies (20-70 days)

NEGATIVE AAO POSITIVE AAO

LAG 0

LAG +5

LAG +10

LAG +15

LAG +20

LAG +25

LAG 0

LAG +5

LAG +10

LAG +15

LAG +20

LAG +25

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Indication that onset of negative phases of AAO is associated with eastward propagation of

the MJO

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Case to Case

Seasonal Variations

Interannual Variations

Long-term Behavior

Time scales

?? ???? ?????? ????????

Extensively studied over the years but no comprehensive theory

Behavior on time scales longer than interannual is unknown

Long-term behavior of the MJO is unknownLong-term behavior of the MJO is unknown

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Has the MJO been more active (linear trend)?

Does the MJO have a low-frequency mode of variability (decadal)?

How will the continuous warming in tropical Indian and Pacific Oceans modify/interact with MJO?

Data• Daily U200 and U850 (1948-2006),

OLR (1979-2006)

• Subtract daily climatology; band-pass filtered (20-200 days)

• Average 15S-15N

• Combined EOF analysis (U200, U850)

• Use (EOF1, PC1), (EOF2, PC2)

• Phase angle (PC1,PC2) normalized

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Wheeler and Hendon (2004)

MJO IdentificationCriteria:oSystematic eastward propagation

at least 1 4 oMinimum amplitude:

A = (PC12 + PC22)1/2 > 0.35oEntire duration between 30-90 daysoMean amplitude during event > 0.9o227 MJO events in 1948-2006

OLR Anomalies

We

st. H

em. &

Afr

ica M

aritim

e Co

ntin

ent

Indian Ocean

Western Pacific

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2 3

4

7 6

8 5

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Linear trends in amplitudes and number of events?

Statistically significant trends in amplitudes and number of MJO

events

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NNR

Average 15S-15N

In progress: are linear trends in MJO activity real?

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Does the MJO have a low-frequency mode of variability?

Low-Frequency diagram

• Consider XT, T=1, N pentads, XT=1 event, XT= 0 no event

• Define moving window SK and compute number of MJO events in SK

• SK odd number and varied from smallest (1 pentad) to largest possible N pentads)

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0

1

2

3

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101 105 109 113 117

SK

Hypothetical Case: events evenly spaced in time

Low-frequency diagram

Cone of Influence

Cone

of In

fluen

ce

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(a)

(b)

Figure 1. (a) Temporal variability of mean MJO amplitudes (linear trend indicated). (b) low-frequency variability of the MJO. (c) Same as in (b), but after removing linear trends. (227 events in 1948-2006)

(c)

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Indication: MJO activity exhibits significant variations on decadal time scales

In progress: stochastic and dynamical models

Simulation with the IPRC University of Hawaii hybrid coupled model (Joshua Fu):

o Atmospheric model: ECHAM

o Oceanic model: intermediate model, tropical Indian and Pacific Oceans

o 200 years simulation

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Figure 4. U200 anomalies phase composites from IPRC_HcGCM 200-yr simulation (782 MJOs).

Identification of model MJO as in observational

analysis

Realistic MJO simulation

Composites of U200 anomalies

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Figure 5. Low-frequency variability of the MJO in the IPRC_HcGCM model (782 MJOs in 200-yrs).

Low-Frequency variations of the MJO200-yr model simulation

Summary

MJO exhibits significant linear trends and decadal variations

reanalysis is affected by changes in observational sampling; impact in MJO characterization is unknown

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www.icess.ucsb.edu/asr

Work in ProgressDeveloping stochastic and dynamical model experiments to investigate trends and low-frequency variations in the MJO Investigating warming in the tropical Indian and Pacific Oceans and their impact in the activity of the MJO

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Real time monitoring and forecasting of the MJO

www.icess.ucsb.edu/asr

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www.cdc.noaa.gov