1. SO442 – the Madden-Julian Oscillation
Lesson 6

2. 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
Now known to be a major propagator of weather systems

3. Atmospheric Scales of Motion
Climate: PDO
Years: ENSO
Seasons: Monsoons
Months/Weeks: MJO
Space and time-scales of dynamical atmospheric processes. SOURCE: UCAR

4. The Madden-Julian Oscillation (MJO)
Important features:
Convectively coupled disturbance that propagates eastward across the Tropics
5-10 m s-1 propagation speed in the Indian and west Pacific, where MJO convective variability is strongly coupled to the large-scale flow.
Simple baroclinic wind structure, with 850 hPa and 200 hPa wind perturbations 180o out of phase
Characteristic timescales of days.
Univ of Munich Physics Dept
Madden and Julian 1972

5. 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

6. The MJO - A Description
A 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

7. MJO Structure in Outgoing Longwave Radiation (OLR):
Indian Ocean and Western Pacific, Phases 1-8
subsidence
component 1 5
convective
component 2 6 3 7 4 8
convective anomaly subsidence anomaly

8. Centered on the equator
Note: in this graphic, the MJO is not one thunderstorm that covers an entire ocean. Such a thing doesn’t exist! Rather, in the region represented by the cloud, MJO favors the development of more thunderstorms than normal
MJO is a very large scale oscillation (approximately 15,000 km east-west distance)
Centered on the equator
Features: one region of upward motion (favoring convection) and one region of downward motion (favoring drier conditions)
climate.gov

9. MJO couplet (one region of upward motion and one region of downward motion) moves eastward along the equator
Why does it move along the equator, and not off the equator?
MJO really is an “equatorally trapped” Kelvin wave
Coriolis force acts to trap the MJO wave along the equator
Over a 3-5 week period, the MJO convective couplet can transit the tropical eastern hemisphere

10. More views of the MJO convective couplet – not just thunderstorms but also specific humidity and wind anomalies, too!
NOAA Pacific Northwest Laboratory (PNL)
Univ of Washington Atmos Sci dept
The passage of the MJO across the tropical oceans also shows up in SST anomalies
US Dept of Energy

11. MJO Cluster Structure
Jon Gottschalck, NOAA Climate Prediction Center

12. MJO Forecasting
Jon Gottschalck, NOAA Climate Prediction Center

13. MJO Forecasting
NOAA Climate Prediction Center

14. How MJO was discovered
In the 1960s and 1970s, new computer power created the ability to look for patterns in meteorological observations.
Could only look for patterns in TIME (at a location), not SPACE (at a given time).
Tended to detect OSCILLATIONS.

15. What They Found
Surface pressure oscillates with a period of days.
ZONAL winds in the lower and upper troposphere also oscillate at this frequency, but 180° out-of-phase.
The signal was limited to the deep tropics.
They found little signal in the meridional wind, or in zonal winds in the midtroposphere.

16. Evidence of MJOs Sea Level Pressure, Equator and 180E, May – Oct 1979
45 days
Figure from R. Madden, 31 Aug 2005

17. Evidence of MJOs
Temperature, Upper Ocean, Equator and 155W, Aug 1991 – Jul 1992
45 days
T 125 m
T 150 m

18. Their Interpretation
MJO is a region of low-level convergence and convection.
Propagating eastward only.
Circumnavigates the globe in days.

19. Their Interpretation
Pressure is LOW in the region of strongest convection.
Upper-level outflow is only in the zonal direction.

20. Circumnavigating the Globe?
Madden and Julian originally believed that this area of convection propagated all the way around the world every days.
But this isn’t exactly right.

21. Circumnavigating the Globe?
Rather, the convection is TRIGGERED in the eastern Indian Ocean (typically by intruding midlatitude systems).
Convection dies out in the eastern Pacific due to cold SSTs

22. Circumnavigating the Globe?
However, the region of upper-level divergence WILL generally travel all the way around the world as a Kelvin Wave.

23. El Nino and the MJO
MJO events can TRIGGER El Nino events by weakening the trade winds (or even having a WESTERLY WIND BURST).

24. El Nino and the MJO Why doesn’t EVERY MJO trigger an El Nino event?
CHARGE/DISCHARGE THEORY:
MJO is the TRIGGER—it happens much more often than the El Nino event itself.
Not every trigger is exactly right.
Even when the trigger is right, maybe ocean conditions are not yet right.
A partial explanation for the timing of ENSO.

25. Triggering MJO Events
An MJO event in the Indian Ocean upsets the SSTs.
It takes time for the SSTs to recover.
Any intruding midlatitude systems during this period will FAIL to trigger an MJO event.
Only when the environment is ready (another days) will the next midlatitude system be able to trigger a new MJO!

26. What are MJO events?
Described by “Nakazawa’s Hierarchy of Convection”

27. What are MJO events?
Each MJO event is actually composed of a small number of “super cloud clusters”--SCCs

28. What are MJO events?
SCCs:
Move EASTWARD
Last a day or two

29. What are MJO events?
What are SCCs?
Made of Cloud Clusters (CCs)

30. What are MJO events? What are CCs? Small groups of thunderstorms
Last less than a day
Move WESTWARD

31. 1 MJO

32. 4 SCCs

33. Many CCs

34. Kelvin waves (15 m s-1) MJO (5 m s-1)
OBSERVATIONS OF KELVIN WAVES AND THE MJO
Time–longitude diagram of CLAUS Tb (2.5S–7.5N), January–April 1987
MJO event from Feb-Mar 1987 seen as cluster of Kelvin waves. Other Kelvin waves were also seen in March & April that were not really part of MJO
Kelvin
waves
(15 m s-1)
MJO
(5 m s-1)

35. OLR power spectrum, 1979–2001 (Symmetric)
How did we know that the cloud clusters in the previous slide were MJO and Kelvin waves? We could calculate their periods and zonal wavenumbers and identify them in this power spectrum diagram
from
Wheeler and Kiladis, 1999

36. Overview of Madden-Julian Oscillations (MJOs)
major and complex disturbances of the global tropical atmosphere-ocean system
propagating intraseasonal (~ 1-2 months) oscillations
usually start in tropical Indian - W Pacific region
have largest amplitude in tropical Indian - Pacific region
propagate E-ward through the tropics
may propagate around globe, especially as UL disturbance
period  days  45 days
zonal wave length  Earth’s circumference
occur throughout the year
may have large impacts on global tropics and extratropics
have impacts on midlatitude climate
strong atmosphere-ocean coupling makes them difficult to analyze and model

37. L H MJOs and Teleconnections
Modeled Tropospheric Response to Western Tropical Pacific
Positive Heating Anomaly in Northern Winter H L
= positive heating
anomaly
= energy propagation
through wave train
= dry air advection
= moist air advection

38. MJOs and Teleconnections
Relationships Between Propagating Tropical Positive Convection Anomaly and North Pacific – North American Circulation and Precipitation Anomalies
cf. Higgins and Mo, J Clim, 1997
Figure from:

39. MJOs and Teleconnections
Z 200 Anomalies, Dec 1996 – Jan 1997
During Dec 96 - Jan 97:
Weak La Nina conditions in tropical Pacific
Intense MJO activity in Indian Ocean – western tropical Pacific
Anomalously heavy precipitation and flooding in N CA, OR, WA
Anomalously low precipitation in SW US
Extratropical wave train similar to expected for MJO convection in
tropical E IO – W Pacific
Other examples of MJO impacts on west coast precipitation?
Jan 92, Feb 93, Jan 95, Oct–Nov 03, Dec 04 – Jan 05, Dec 05 - Jan 06

40. Composites for: Phase 3, All Amplitudes, and all Background States, by Season
OND
JFM
ONDJFM
NPNA response to MJO affected by season. Effects can be dramatic. Likely causes: seasonal changes in location of convection and subsidence, and in strength, location, shear of east Asia - North Pacific jet.

41. Favorable and Unfavorable Factors for Wet and Dry Conditions in California
Favorable / Unfavorable Conditions for MJO-Associated
Anomalously Wet Conditions in CA
Favorable
Unfavorable
1. Early or late phases of the MJO
2. OND or JFM
3. El Niño or neutral background state
4. Wave train from Asia with anomalous
low north and west of CA
5. Southwest to northeast tilt to the anomalous low off CA
1. La Niña background state
2. Middle phases of the MJO
Anomalously Dry Conditions in CA
1. Middle or late phases of the MJO
2. JFM
3. La Niña background state
4. Anomalous high over northeastern Pacific
1. Early phases of the MJO
2. El Nino background state
Corresponding results for PNW, BC, and AK regions (not shown)

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

43. Simplified Madden-Julian Oscillation Composite
OLR from A.J. Matthews, 2000.

44. Decay Region
Formation
Region

45. Active
Convection

46. Enhanced
Easterlies
Active
Convection

47. Cold air outbreak enhancement
Active
Convection

48. Deflected
Jet Stream
Active
Convection
Energy Build-up

49. MJO - A Modeler’s Nightmare
GCM simulation of convection (CPS)
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

50. Theory: Moisture Modes and the MSE Budget
A moisture mode instability can result if large-scale divergent motions associated with convection import MSE into the column (e.g. Raymond et al. 2009, negative gross moist stability)
Alternatively, export by divergent motions can be positive, but MSE sources such as latent heat flux and cloud-radiative feedbacks overcompensate to produce MSE increases as a result of convection.
Such instability is manifest for WTG as strong positive moisture-convection feedbacks
Peters and
Bretherton (2006)

51. Madden-Julian Oscillation
(a.k.a. Intraseasonal, 40-50, Day Oscillation)
Intraseasonal Time Scale: ~40-60 days
Planetary-Scale: Zonal Wavenumbers 1-3
Baroclinic Wind Structure
Eastward Propagation
E. Hem: ~5 m/s, Surf.+Conv.+Circ. Interactions
W. Hem: ~ > 10 m/s, ~Free Tropospheric Wave
Tendency to be Equatorially Trapped
Strong Seasonal Dependence:
NH Winter: Eastward Propagation
NH Summer: ~Northeast Propagation
Significant Interannual Variability
Potential Role of Ocean/SST Feedback
Convection Has Multi-Scale Structure
Significant Remote and Extra-Tropical Impacts
U200
U850
Cloudy
Low OLR
Clear
High OLR
Rainfall
Typical Variables Used for MJO Analysis
1987/88
Madden & Julian, 1972

52. A Typical MJO in N.H. Winter
Composite rainfall maps derived from merged satellite and in-situ measurements are separated by 10 days.
Rainfall anomalies propagate in a eastward fashion and mainly affect the Tropical eastern hemisphere.
These anomalies are accompanied by anomalies in wind, solar radiation, sea surface temperature, etc.
5 stages of the wet/dry anomalies of the MJO in boreal winter: (1) initiation, (2) eastward propagation in the Indian Ocean, (3) weakening over the Marine Continent, (4) formation of new convection in the western equatorial Pacific and propagates eastward, and (5) die out n the central Pacific. Each stage lasts about 8 days.

53. A Typical MJO in N.H. Summer3
A Typical MJO in N.H. Summer 4
Composite rainfall maps derived from merged satellite and in-situ measurements are separated by 10 days.
Rainfall anomalies propagate in a northeast fashion and mainly affect the Tropical eastern hemisphere.
These anomalies are accompanied by anomalies in wind, solar radiation, sea surface temperature, etc. 5 1
The MJO undergoes a strong seasonal cycle in both its strength and latitudinal locations [Madden, 1986; Gutzler and Madden, 1989; Salby and Hendon, 1994; Zhang and Dong, 2004], as illustrated in Figures 9 and 10. Its primary peak season is austral summer/fall when the strongest MJO signals are immediately south of the equator; the second peak season is boreal summer when its strongest signals are north of the equator. The primary peak season in austral summer is related to the Australian summer monsoon [Hendon and Liebmann, 1990], while the secondary peak season in boreal summer is related to the Asian summer monsoon [e.g., Lawrence and Webster, 2002]. 2

54. Boreal Summer Complex Propagation & Multi-Scale Organization1 2 3 4 5
Eastward Propagating
Convective Envelope
~40-50 days
Westward Propagating
Rossby-Waves
~ day;
Modulated by 40-50day
Kemball-Cook & Wang, 2001
Northward Propagation
Of Rossby-Wave Convection
(twisting, SST, moisture feedback)