Madden-Julian Oscillation #2
Sunday, 16. December 2007, 11:47:23
In my latest post I mentioned that the Madden-Julian Oscillation, or in short MJO might serve as tool to extend the weather forecasts beyond the usual 5 days.
The MJO is a cyclical wave in Earth’s atmosphere - a cyclical pattern of slow, eastward-moving waves of clouds, rainfall and large-scale atmospheric circulation anomalies that can strongly influence long-term weather patterns around the world. It is a 30-to-90-day cycle, and it spans nearly half of Earth's equator, primarily over the Indian Ocean and western Pacific. The MJO affects precipitation over the tropical monsoon regions. It affects the winter jet stream and atmospheric circulation in the Pacific/North America region, causing anomalies that can lead to extreme rainfall events. It can also change summer rainfall patterns in Mexico and South America and may trigger El Niño events.
Fortunately it now seems possible to predict the MJO itself according to an article in Science of 14 December 2007, titled A Madden-Julian Oscillation Event Realistically Simulated by a Global Cloud-Resolving Model. The results of the study demonstrate the potential making of month-long MJO predictions when global cloudresolving models with realistic initial conditions are used. The predictions are based on infrared satellite images of clouds. It is indeed expected that weather forecasts beyond 10 days could be improved if the MJO representations in global weather prediction models were more realistic.
Another article in the same issue of Science titled Deep Ocean Impact of a Madden-Julian Oscillation Observed by Argo Floats shows that these atmospheric waves also affect the oceans - and to a greater depth than previously known. The authors 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 at least 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.
Argo floats are described here. and the use of these floats in oceanic studies mentioned in an editorial in Science of 15 December 2006. I wrote about oceanic Kelvin waves here.
Oceanic equatorial Kelvin waves in the central and eastern Pacific are forced by MJO wind stress anomalies. The MJO can also influence the deep ocean in high latitudes and has has a direct impact on the ocean biosphere, with implications for the fishing industry.
• http://www.sciencemag.org/cgi/content/short/318/5857/1763
• http://www.sciencemag.org/cgi/content/short/318/5857/1765
• http://www.sciencemag.org/cgi/content/summary/314/5806/1657
• http://www.argo.ucsd.edu/
The MJO is a cyclical wave in Earth’s atmosphere - a cyclical pattern of slow, eastward-moving waves of clouds, rainfall and large-scale atmospheric circulation anomalies that can strongly influence long-term weather patterns around the world. It is a 30-to-90-day cycle, and it spans nearly half of Earth's equator, primarily over the Indian Ocean and western Pacific. The MJO affects precipitation over the tropical monsoon regions. It affects the winter jet stream and atmospheric circulation in the Pacific/North America region, causing anomalies that can lead to extreme rainfall events. It can also change summer rainfall patterns in Mexico and South America and may trigger El Niño events.
Fortunately it now seems possible to predict the MJO itself according to an article in Science of 14 December 2007, titled A Madden-Julian Oscillation Event Realistically Simulated by a Global Cloud-Resolving Model. The results of the study demonstrate the potential making of month-long MJO predictions when global cloudresolving models with realistic initial conditions are used. The predictions are based on infrared satellite images of clouds. It is indeed expected that weather forecasts beyond 10 days could be improved if the MJO representations in global weather prediction models were more realistic.
Another article in the same issue of Science titled Deep Ocean Impact of a Madden-Julian Oscillation Observed by Argo Floats shows that these atmospheric waves also affect the oceans - and to a greater depth than previously known. The authors 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 at least 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.
Argo floats are described here. and the use of these floats in oceanic studies mentioned in an editorial in Science of 15 December 2006. I wrote about oceanic Kelvin waves here.
Oceanic equatorial Kelvin waves in the central and eastern Pacific are forced by MJO wind stress anomalies. The MJO can also influence the deep ocean in high latitudes and has has a direct impact on the ocean biosphere, with implications for the fishing industry.
• http://www.sciencemag.org/cgi/content/short/318/5857/1763
• http://www.sciencemag.org/cgi/content/short/318/5857/1765
• http://www.sciencemag.org/cgi/content/summary/314/5806/1657
• http://www.argo.ucsd.edu/
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