June 3, 2011 | A new study led by NCAR’s Wei Yu and CU-Boulder’s Weiqing Han looks at the effects of the Madden-Julian Oscillation (MJO), with a focus on the tropical Atlantic Ocean.

The MJO is a disturbance of the tropical atmosphere with pulses that typically originate in the Indian Ocean every 30 to 60 days and travel eastward. It is the largest source of intraseasonal (within one season) variability in the tropics, causing wet and dry periods to alternate. The MJO also affects weather and climate beyond the tropics.

The researchers focused on an event in 2002 in which variations in surface winds and other indicators on a timescale of 40–60 days occurred in the tropical Atlantic. Using observations from satellites, they found that these wind variations resulted largely from the MJO, which they show propagated eastward from the Indian and Pacific oceans to the Atlantic during the winter and spring of 2002. According to the study, the Isthmus of Panama appears to be the dominant pathway for the surface wind anomalies to reach the Atlantic.

The study adds to scientists’ body of knowledge about how the MJO propagates around the globe. Previous research has shown that the MJO can influence a number of weather patterns, including El Niño, the Asian-Australian monsoon, the Indian Ocean Dipole, the North American monsoon, and tropical cyclones.

Future work will look at whether the MJO played a role in how El Niño affected the Atlantic in 2002.

Yu, W., W. Han, E. D. Maloney, D. Gochis, and S.-P. Xie (2011), "Observations of eastward propagation of atmospheric intraseasonal oscillations from the Pacific to the Atlantic," Journal of Geophysical Research, 116, D02101, doi:10.1029/2010JD014336

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