Skip to main content

What is the MJO, and why do we care?

The articles posted on this blog have described ENSO, its regional and global impacts, and the challenge of forecasting it, among several other topics. Here we introduce another important player on the tropical stage: the Madden-Julian Oscillation, or MJO. While the MJO is a lesser-known phenomenon, it can have dramatic impacts in the mid-latitudes. Several times a year the MJO is a strong contributor to various extreme events in the United States, including Arctic air outbreaks during the winter months across the central and eastern portions of the United States.

So what is the MJO?

Imagine ENSO as a person riding a stationary exercise bike in the middle of a stage all day long. His unchanging location is associated with the persistent changes in tropical rainfall and winds that we have previously described as being linked to ENSO. Now imagine another bike rider entering the stage on the left and pedaling slowly across the stage, passing the stationary bike (ENSO), and exiting the stage at the right. This bike rider we will call the MJO and he/she may cross the stage from left to right several times during the show.

So, unlike ENSO, which is stationary, the MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average. This atmospheric disturbance is distinct from ENSO, which once established, is associated with persistent features that last several seasons or longer over the Pacific Ocean basin. There can be multiple MJO events within a season, and so the MJO is best described as intraseasonal tropical climate variability (i.e. varies on a week-to-week basis).

The MJO was first discovered in the early 1970s by Dr. Roland Madden and Dr. Paul Julian when they were studying tropical wind and pressure patterns. They often noticed regular oscillations in winds (as defined from departures from average) between Singapore and Canton Island in the west central equatorial Pacific (Madden and Julian, 1971; 1972; Zhang, 2005).

The MJO consists of two parts, or phases: one is the enhanced rainfall (or convective) phase and the other is the suppressed rainfall phase. Strong MJO activity often dissects the planet into halves: one half within the enhanced convective phase and the other half in the suppressed convective phase. These two phases produce opposite changes in clouds and rainfall and this entire dipole (i.e., having two main opposing centers of action) propagates eastward. The location of the convective phases are often grouped into geographically based stages that climate scientists number 1-8 as shown in Figure 1.

Rainfall anomalies

Figure 1: Difference from average rainfall for all MJO events from 1979-2012 for November-March for the eight phases described in the text. The green shading denotes above-average rainfall, and the brown shading shows below-average rainfall. To first order, the green shading areas correspond to the extent of the enhanced convective phase of the MJO and the brown shading areas correspond to the extent of the suppressed convective phase of the MJO. Note eastward shifting of shaded areas with each successive numbered phase as you view the figure from top to bottom.

 

For the MJO to be considered active, this dipole of enhanced/suppressed convective phases must be present and shifting eastward with time. An animated illustration that depicts the global scale and eastward propagation of these two phases of the MJO is shown here (Fig. 2: animation).

MJO animation

Figure 2. An animation illustrating the organization of the MJO into its enhanced and suppressed convective phases during an MJO event during the spring of 2005. The green shading denotes conditions favorable for large-scale enhanced rainfall, and the brown shading shows conditions unfavorable for rainfall. The MJO becomes organized during late March through May as the green shading covers one half of the planet, and brown shades the other half all along as these areas move west to east with time. Notice how the shading returns to the same location on the order of about 45 days.

 

What’s behind the pattern?

Let’s dig a little deeper and look at some of the characteristics within these two convective phases (Figure 3). In the enhanced convective phase, winds at the surface converge, and air is pushed up throughout the atmosphere. At the top of the atmosphere, the winds reverse (i.e., diverge). Such rising air motion in the atmosphere tends to increase condensation and rainfall.

MJO diagram

The surface and upper-atmosphere structure of the MJO for a period when the enhanced convective phase (thunderstorm cloud) is centered across the Indian Ocean and the suppressed convective phase is centered over the west-central Pacific Ocean. Horizontal arrows pointing left represent wind departures from average that are easterly, and arrows pointing right represent wind departures from average that are westerly. The entire system shifts eastward over time, eventually circling the globe and returning to its point of origin. Climate.gov drawing by Fiona Martin.

In the suppressed convective phase, winds converge at the top of the atmosphere, forcing air to sink and, later, to diverge at the surface (Rui and Wang, 1990). As air sinks from high altitudes, it warms and dries, which suppresses rainfall.

It is this entire dipole structure, illustrated in Figure 3, that moves west to east with time in the Tropics, causing more cloudiness, rainfall, and even storminess in the enhanced convective phase, and more sunshine and dryness in the suppressed convective phase.  

The changes in rainfall and winds described above impact both the Tropics and the Extratropics, which makes the MJO important for extended-range weather and climate prediction over the U.S. and many other areas. The MJO can modulate the timing and strength of monsoons (e.g., Jones and Carvalho, 2002; Lavender and Matthews, 2009), influence tropical cyclone numbers and strength in nearly all ocean basins (e.g., Maloney and Hartmann, 2000), and result in jet stream changes that can lead to cold air outbreaks, extreme heat events, and flooding rains over the United States and North America (Higgins et al. 2000, Cassou, 2008, Lin et al. 2009, Zhou et al., 2012, Riddle et al., 2013, Johnson et al., 2014).

The MJO can produce impacts similar to those of ENSO, but which appear only in weekly averages before changing, rather than persisting and therefore appearing in seasonal averages as is the case for ENSO.

Future posts will focus on the details of how we monitor and assess the strength of the MJO, provide details on impacts and the reasons for those impacts, and describe the current state of MJO predictability.  Realtime MJO information that is updated daily or weekly can be found on the NOAA CPC MJO webpage.

References

Madden R. and P. Julian, 1971: Detection of a 40-50 day oscillation in the zonal wind in the tropical Pacific, J. Atmos. Sci., 28, 702-708.

Madden R. and P. Julian, 1972: Description of global-scale circulation cells in the tropics with a 40-50 day period. J. Atmos. Sci., 29, 1109-1123.

Cassou, C., 2008: Intraseasonal interaction between the Madden Julian Oscillation and the North Atlantic Oscillation. Nature, 455, 523-527 doi:10.1038/nature07286 Letter

Higgins, W., J. Schemm, W. Shi, and A. Leetmaa, 2000: Extreme precipitation events in the western United States related to tropical forcing. J. Climate, 13, 793-820.

Nathaniel C. Johnson, Dan C. Collins, Steven B. Feldstein, Michelle L. L’Heureux, and Emily E. Riddle, 2014: Skillful Wintertime North American Temperature Forecasts out to 4 Weeks Based on the State of ENSO and the MJO*. Wea. Forecasting29, 23–38.

Jones, C. and L. Carvalho, 2002: Active and Break phases in the South American Monsoon System.  J. Climate, 15, 905-914.

Lavender, S. and A. Matthews, 2009: Response of the West African monsoon to the Madden-Julian Oscillation, J. Climate, 22, 4097-4116.

Maloney E. and D. Hartmann, 2000: Modulation of hurricane activity in the Gulf of Mexico by the Madden-Julian Oscillation. Science, 287, 2002-2004.

Riddle, E. E., M. B. Stoner, N. C. Johnson, M. L. L’Heureux, D. C. Collins, and S. B. Feldstein, 2013: The impact of the MJO on clusters of wintertime circulation anomalies over the North American region. Climate Dyn.40, 1749–1766.

Zhang, C., 2005: Madden-Julian Oscillation. Reviews of Geophysics, 43, 1-36.

Zhou S., M. L’Heureux, S. Weaver, and A. Kumar, 2012: A composite study of MJO influence on the surface air temperature and precipitation over the Continental United States. Climate Dyn., 38, 1459-1471.

 

Lead reviewer: Anthony Barnston

Comments

I think I understand, more or less, how the MJO works. Air rises in one half of the world, so air must fall in the other half. This makes plenty of sense, so much sense that I want to know why this isn't ALWAYS the case. What conditions result in an in-active MJO pattern?

From the author of this post, Jon Gottschalck:

"This is a very good question. Perhaps an alternative or better way to answer this question is that we still don't understand why and how the MJO initiates, maintains itself or decays in the manner described here. There are many theories which I won't go into detail here but no one theory completely explains the unique characteristics that we observe with respect to its period, propagation speed or large global scale. An international field campaign centered across the Indian Ocean called DYNAMO (Dynamics of the MJO) took place from October 2011 through March 2012 in which a wealth of data was collected during a period of robust MJO activity. It is hoped that research using this data in coming years will advance the science of why the MJO behaves the way it does."

Interesting. We still don't understand why and how the MJO initiates, maintains itself or decays? besides stating the obvious that warm rises and cold air sinks, almost half a century later after MJO was first identified in early 1970s by Madden and Julian. Funny! When do you think you people will understand! :-)

There is no way to predict with much confidence when people will understand why and how the MJO iitiates, maintains itself or decays. Increases in understanding usually occur incrementally and over fairly long periods of time. It might seem like we are stupid, or are not trying hard enough, but that is not the case. The questions are HARD. There are remaining questions about ENSO that are also very difficult. They are as hard as those about why we still don't have a way of preventing the common cold.

Has there ever been an MJO event on the eastern Pacific like in the Baja Mexico area? Just wondering, as the blob seems to be an anomaly of interest this year.

The MJO itself is fairly well constrained to the tropics, although some of its impacts do extend away from the tropics, in both northern and southern hemispheres. The blob is happening in the northern hemisphere, and has been there for a few months. The MJO effects usually follow the MJO itself, progressing from west to east around the globe, unlike the blob which has been relatively stationary. Also, the MJO effects are more easily observed in the atmosphere than the ocean, because it takes longer for the ocean to respond (especially in terms of its surface and subsurface temperature, which mainly define the blob). While there is an effect on the ocean temperature, especially in the tropics, it is not a very large effect because the influence of the MJO keeps changing too quickly. So, the blob is likely mainly related to something other than the MJO, such as the ENSO condition or even the PDO condition preceding its formation. Or, it may not be obviously related to any familiar phenomena and may be "its own thing" to large measure.

Well here we are a few years later and MJO is quite string right now from what I hear causing a weakening of trade winds. "Upstream", if you will, from the trades are the "Westerlies" into Oregon and along California. Spring time, just around the corner, is when we usually get the strongest westerlies which cause a large amount of up-welling. It's why we have a lot of good fish, and the animals that eat them. If the winds don't come, our local coastal waters will again heat up. Interesting times....

I'm very glad to have found this article as I'm trying to learn as much as I can about world weather and the various states associated with such. I live in here in Southern California and as you might guess, there is quite the discussion on this strong El Nino. Now given the ENSO conditions as they currently stand, it would seem that the MJO can either strengthen or weaken its affects and given the 30-60 day phase cycle of the MJO, this would appear to happen at least a couple of times during the ENSO cycle. The question is whether or not such research has been performed to determine if this occurs? My next question is whether or not we know the effect that the MJO has on the Jet stream in the Mid Latitudes? You described that the MJO is related to the Tropics and not the mid latitudes? When we have a ridge of high pressure to the east of us, it creates very dry conditions (and we are in a drought here). I know that there is a specific weather reason as to why this long-lasting ridge develops. Regarding the MJO, My thought is similar to the gravitational effects of the moon on the tides. The high tide does not line up with the moon directly overhead as there is a lagged effect, but it is clear the moon affects the tides (ok, I know that we are not discussing gravitational effects, but given the Earth is a closed system, I have this gut feeling that these cycles being discussed do somehow correlate to a greater or lesser degree. This is a fascinating discussion for me and thank you in advance for any potential response!

Thank you very much for your article. Brightening. Is there any insight on why the MJO is moving eastwards?

I'd like to share my latest co-authored publication: Impacts of the Madden-Julian oscillation on intraseasonal precipitation over Northeast Brazil (NEB). In this article we discuss the MJO impacts over NEB for all four seasons, providing the magnitude and signs of the rainfall anomalies for each season and MJO phase. DOI: 10.1002/joc.4818 https://goo.gl/5oh6uE http://onlinelibrary.wiley.com/doi/10.1002/joc.4818/abstract

The Weather Pattern in 2016 has been very volatile. Forecast Models seem to change weekly. Are the remnants of the Super El Nino still impacting Global Weather to an extent? And if so, could the after-effect of the Super El Nino have a influence on the MJO? Thanks!

MJO is measured as an intra-seasonal oscillation and ENSO as interannual oscillation.How can we link MJO with ENSO? Can we measure somehow interannual response of MJO that can directly explain ENSO or its triggering mechanism?

Many atmospheric weather phenomena can act as stochastic forcing to ENSO.  The most effective one is strong episodes of surface westerly wind, often referred to as westerly wind bursts (WWB) or westerly wind events (WWE).  The strongest, long-lasting and eastward moving equatorial WWE are mostly associated with the MJO. Many observations have shown anomalously strong MJO activities prior to and during the onset of ENSO warm events.  Numerous journal articles explore in greater detail the relationship between ENSO and the MJO. 

Are these correlation plots published in any of the references above? Thanks!

Your bicycle analogy is not helpful. Nor is your animation. If the MJO is measured routinely and systematically, why not show exactly which lats and longs this is done? If the MJO occurs from November through March, why does your animation focus on February through June? Moreover, I don't find that the jerky animation demonstrates a smooth eastward migration of moisture within the tropics. But you have the platform, so unless you can be more definitive, I guess the MJO can continue to be whatever you say it is. I will be posting as I continue to ask questions. Mike Wallace, Hydroclimatologist.

The ENSO bloggers have a limited amount of time they can devote to moderating comments. This means they are committed to handling questions and comments on posts for a week or so after they are initially published, but not in perpetuity. Comments may be approved and published in case other readers want to have a discussion, but you're unlikely to hear from one of the experts on a post this old. Note that I did see your other comment about there being a frame out of order in the animated gif, and I was able to find the file and correct it.  

Your incomprehensible coverage of the MJO can also be seen in the animation, where you have a June 12 frame between May 8 and May 13. Probably best that you at least correct that.

Normally the Equatorial Trough shifts south and then begins to return north between November and March for any given year. But your image series doesn't appear to show any meridional changes. Why is that? What is the actual date span of each frame and are the increments constant? I'm saving this request and will include it in my post at abeqas under title "maddening-julian-oscillation" Please send me the traceable source citation for each frame of Figure 1. Please consider this a FOIA request if you choose to otherwise disregard. Please include the actual calendar spans for each frame (ie. Nov #-#, Nov 3-Dec#). Mike Wallace. P.S. I note from above comment that this site is current and actively maintained.

Can someone explain me how to interpret MJO phase diagram?

As far as I can see, the shadings denote deviation from the (climatologically) normal rainfall amounts. Green and blue means more rain, brown means less. You see that the blue spot is moving East, and with it the surrounding green / trailing brown areas. The whole pattern travels around Earth in 30 to 60 days. Does that help? Jens

In reply to by Dr. MM Ali

The article starts out with an acronym but does not define it for the readers. WHAT IS ENSO ? Please, do not throw guvment acronyms at the public without defining them !

ENSO = El Nino Southern Oscillation. For a start, look at https://en.wikipedia.org/wiki/El_Niño–Southern_Oscillation Hope that helps :)

In reply to by Ralph Yost

Hi Ali,

So the mjo has 8 phases correlating to that diagram. Think of them as almost locations. When the MJO enters those phases, it can mean different impacts on weather/climate across the globe including the US.

In reply to by Ali

In our experience the MJO can start from anywhere, though deep convection is not evident over land masses like Africa... the convective part becomes more prominent as the wave transverses the Indian Ocean and Indonesia b/c the ocean is a source of heat/moisture.  

In reply to by Aakash Majumdar

Thanks. Another thing is that.. When MJO enters in the inner circle of the RMM .. what does it mean? How can this phase reverse it's direction .. As it rotates in anti clockwise direction..

When the MJO is in the inner circle of the RMM that means that the MJO signal is not strong or is nonexistent. Other climate phenomena can also show up on that diagram that can give the impression that the MJO is going backwards or forwards or any which way, but doesn't necessarily mean that what is being seen is an MJO.

The dynamics of the MJO are still not completely understood, so there are a lot details that still need to be worked out. But in general, the eastward propagation relates to how the atmospheric circulation responds to the anomalies of atmospheric convection (the regions of enhanced and suppressed rainfall). Under one framework, the eastward propagation can be understood as a response to the atmospheric Rossby waves forming to the west of the enhanced convection and atmospheric Kelvin waves to the east. The Rossby waves lead to eastward winds while the Kelvin waves lead to westward winds that converge east of the enhanced convection. This converging air rises to the east of the original enhanced convection, leading to new convection and an eastward progression of the whole MJO system.

Add new comment