Madden-Julian Oscillation

The Madden-Julian Oscillation (MJO), also known as the 40-day wave, is a large scale oscillation (wave) in the equatorial region. The MJO originates over the Indian Ocean and travels east at 800 km per day (10m/s). The information presented here builds on the analysis presented in Donald, A., H. Meinke, B. Power, A. de H. N. Maia, M. C. Wheeler, N. White, R. C. Stone, and J. Ribbe (2006), Near-global impact of the Madden-Julian Oscillation on rainfall, Geophys. Res. Lett., 33, L09704, doi:10.1029/2005GL025155.

Current Situation Report

The MJO is currently in phase 1 The impact of this on Austral Winter rainfall is shown below:
rainfall effect.		 The 40 day Phase Diagram (Spiderweb) is shown below:
spider.

The MJO information was last updated on: 1/ 7/2008: (1, 1.600290) .


This animation illustrates the eastward movement and location of the MJO (the large red oval represents the possible locations of the centre of the MJO) in the tropics, and its cyclic nature. The Real Time Multivarite MJO (RMM) phases are defined by Matthew Wheeler of the BMRC (link), and have been used here to define the MJO. The RMM Index divides the eastern hemisphere passage of the MJO into 8 phases, that correspond with the location of convection (rainfall) in the tropics. Phase 1 may be indicate both the initiation of an MJO cycle over the Indian Ocean, and/or the breakdown of convection over the mid Pacific Ocean (the MJO is cyclic). The MJO does exist beyond the geographical limits of these 8 phases, but dries out, and it is not associated with convection (rainfall), so the 8 RMM phases encompass our area of interest in the MJO.

We have found that the location of the MJO, or phase, is linked with patterns in Australia's rainfall. This validates anecdotal evidence about the effect of the MJO recognised by many in the rural sector. We performed statistical tests on rainfall data, and can show when and where regions of Australia may experience enhanced or suppressed conditions, based on the phase of the MJO. Other synoptic factors ultimately determine rainfall, but these results can help you to forecast the increased chance of rain as an MJO traverses the tropics.

Enhanced and Suppressed Rainfall

The rainfall maps show patterns of enhanced (blue) and suppressed (red) rainfall. This refers to statistical tests of rainfall distribution based on the 8 phases of the MJO. If the rainfall distribution is shifted toward more rain during an MJO phase, then the station is coloured blue. Conversely, if the rainfall distribution is shifted toward less rain (zero), then the station is coloured red. If there is no significant shift in the distribution, then the stations are left blank. For example, there is a shift in the rainfal distribution towatd more rain for many stations in eastern NSW during Austral summer Phase 5, during Austral Phase 2 many of the same stations exhibit a shift towards less rain than the normal (all MJO phases)rainfall distribution for that area, and during Austral phase 8, the rainfall distribution is much the same independant of the phase of the MJO.

While the size of the difference of the rainfall distribution is relflected by the depth of colour, rainfall distributions are different at each station, and so at this stage the size of the distribution is not potrayed as an amount (mm) of rainfall difference. For example (in Australia), a big shift in the distibution of rainfall in an arid area may result from ifferent rainfall amounts to a shift in rainfall distribution attributed to the MJO in a coastal region.

At any time we know the value of the RMM Index phase. Hence, we can forecast the movement of the MJO along the equator.Using the maps provided for each of the 8 phases, you can use this information to determine whether there is an increased or decreased probability of receiving rain at your location of interest. This forecast is based on our understanding of the movement of the MJO and its impact on broad-scale synoptic patterns. For example, in early February 2004 the MJO phase 4 was associated with substantial rains over much of Qld and northern NSW (see satellite picture below).

This is an experimental site showing research in progress. So far, this work has been financially supported by DPI&F, Grains Research and Development Corporation (GRDC; DAQ469) and the Cotton Research and Development Corporation (CRDC; DAQ104C)

We need to further investigate (a) seasonal MJO impacts and (b) connection between MJO and ENSO impacts and (c) influences of the MJO on temperature variability. We are recieving funding from L&W via their MCV program. We will need to attract further funding to conduct future MJO research.

Near-Global Impact Of The Madden-Julian Oscillation On Rainfall. Alexis Donald, Holger Meinke, Brendan Power, Aline de H. N. Maia, Matthew C. Wheeler, Neil White, Roger C. Stone and Joachim Ribbe. Geophysical Research Letters, 33, L09704, doi:10.1029/2005GL025155. Copyright [2006] American Geophysical Union. Further reproduction or electronic distribution is not permitted.