Variations in the Activity of the Madden-Julian Oscillation:

1. Variations in the Activity of the Madden-Julian Oscillation: Implications for the Southern Hemisphere Charles Jones University of California Santa Barbara Collaboration: Leila Carvalho (USP)

2. Outline • Brief overview of the MJO • Example of importance of the MJO for the midlatitudes of the southern hemisphere • Outstanding issues about the MJO

3. The Madden-Julian Oscillation 1958-2006 • Originally discovered in early 1970’s • Most important mode of tropical intraseasonal variations • Time scales of 30to60 days • Anomalies propagate eastward along the tropical belt; phase speeds ~ 5 m s-1 • Eastern hemisphere: stronginteractionwith clouds, rain, surface winds and large-scale circulation • Western hemisphere: modestinteractionwith convection and large-scale circulation • Significant case-to-caseand interannual variability Power spectrum of zonal winds at 850-hPa 30-60 days

4. Major MJO Climate Influences • 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

5. Madden-Julian Oscillation (MJO) Life Cycle -15 Days Eastward propagation of enhanced Convection -5 Days Time 5 Days 15 Days Hendon and Salby (1994)

6. Madden-Julian Oscillation (MJO) Life Cycle Anomalous upper level circulation (200-hPa) Coupled Forced Rossby-Kelvin wave response Rossby waves Kelvin wave + - - + Enhanced Convection in the western Pacific Midlatitude wave train

7. Example of importance of MJO for Southern Hemisphere Variability 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 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

8. 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.

9. 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

10. Extratropical Cyclones properties – Obtained from tracking scheme based on Murray and Simmonds (1991) Minimum Pressure Maximum latitude AAO- AAO- AAO+ AAO+ Life cycle duration * 12 h Carvalho et al. 2005 AAO- AAO+

11. What are the relationships between the MJO and AAO?

12. Lag composites (Days) OLR anomalies (20-70 days) NEGATIVE AAO POSITIVE AAO LAG 0 LAG 0 LAG +5 LAG +5 LAG +10 LAG +10 LAG +15 LAG +15 LAG +20 LAG +20 LAG +25 LAG +25

13. Indication that onset of negative phases of AAO is associated with eastward propagation of the MJO

14. Fundamental questions about the MJO • Extensively studied over the years but no comprehensive theory • Behavior on time scales longer than interannual is unknown Case to Case Seasonal Variations Interannual Variations Long-term Behavior Time scales ??? ???? ? ?? Long-term behavior of the MJO is unknown

15. 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?

16. Typical MJO: 12 34 5 67 8 • 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 Wheeler and Hendon (2004)

17. OLR Anomalies • MJO Identification • Criteria: • Systematic eastward propagation • at least 1 4 • Minimum amplitude: • A = (PC12 + PC22)1/2 > 0.35 • Entire duration between 30-90 days • Mean amplitude during event > 0.9 • 227 MJO events in 1948-2006 Western Pacific 7 6 8 5 West. Hem. & Africa Maritime Continent 1 4 2 3 Indian Ocean

18. Linear trends in amplitudes and number of events? Statistically significant trends in amplitudes and number of MJO events

19. In progress: are linear trends in MJO activity real? NNR Average 15S-15N

20. 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)

21. Hypothetical Case: events evenly spaced in time SK Low-frequency diagram Cone of Influence Cone of Influence

23. 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): • Atmospheric model: ECHAM • Oceanic model: intermediate model, tropical Indian and Pacific Oceans • 200 years simulation

24. Identification of model MJO as in observational analysis Realistic MJO simulation Composites of U200 anomalies

25. Low-Frequency variations of the MJO 200-yr model simulation

26. Summary • MJO exhibits significant linear trends and decadal variations • reanalysis is affected by changes in observational sampling; impact in MJO characterization is unknown • Work in Progress • Developing 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 • www.icess.ucsb.edu/asr

27. Real time monitoring and forecasting of the MJO • www.icess.ucsb.edu/asr

28. www.cdc.noaa.gov