Deeper Understanding of the MJO

 

The Madden-Julian Oscillation (MJO) is a large-scale (1000-kilometer) atmospheric disturbance that propagates slowly eastward through the tropics from the Indian Ocean to the western Pacific during the course of 30 to 60 days. The MJO affects precipitation over the tropical monsoon regions and has been implicated as a trigger of El Niño-Southern Oscillation events.

 

It is coupled with the upper ocean through its effects on surface fluxes of solar radiation caused by changes in cloudiness, and on evaporation from the ocean surface caused by surface wind speed changes, which can heat or cool the ocean mixed layer

by up to 1°C during a strong MJO event.

 

Nonetheless, important aspects of the MJO still are unclear, such as how deep into the ocean its influence extends, in part because the range of scales of the processes it involves have made it difficult to simulate in models (see the Perspective by Hartmann and Hendon).

 

Matthews et al. (p. 1765) used a data set of unprecedented size obtained from autonomous, free-drifting instruments, called Argo floats, to show that the surface wind stress associated with the MJO can force eastward-propagating oceanic Kelvin waves that extend to a depth of 1500 meters and that have amplitudes of as much as six times those of annual-cycle Kelvin waves.

 

These amplitudes are significantly greater than those predicted by ocean models, so that the MJO could affect a much larger volume of the Pacific Ocean than just the ocean surface. Miura et al. (p. 1763) address one of the shortcomings of contemporary global meteorological models--cumulus cloud parameterization--by using a model that allows direct coupling of atmospheric circulation and clouds to simulate an MJO event. Their results show that MJO predictions extending 1 month into the future soon may be possible.

 

This Week in SCIENCE, Volume 318, Issue 5857

dated December 14 2007

Welcome back Fred! Is there anything about this that you would like to discuss?

 

Like, how this could affect later local weather (not climate) prediction models, or anything global warming related, or what this implies for the people who live in the southern and tropical regions where this effect takes place, or what exactly?

There's already a bit of 'worry' about the land changes occuring in Asia (the plateau region too, and the glaciers), and Indonesia, etc. The monsoon is under threat, apparently.