Details

Autor(en) / Beteiligte

• Zhang, C.
• Adames, Á. F.
• Khouider, B.
• Wang, B.
• Yang, D.

Titel

Four Theories of the Madden‐Julian Oscillation

Ist Teil von

• Reviews of geophysics (1985), 2020-09, Vol.58 (3), p.e2019RG000685-n/a

Ort / Verlag

United States: Blackwell Publishing Ltd

Erscheinungsjahr

2020

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• Studies of the Madden‐Julian Oscillation (MJO) have progressed considerably during the past decades in observations, numerical modeling, and theoretical understanding. Many theoretical attempts have been made to identify the most essential processes responsible for the existence of the MJO. Criteria are proposed to separate a hypothesis from a theory (based on the first principles with quantitative and testable assumptions, able to predict quantitatively the fundamental scales and eastward propagation of the MJO). Four MJO theories are selected to be summarized and compared in this article: the skeleton theory, moisture‐mode theory, gravity‐wave theory, and trio‐interaction theory of the MJO. These four MJO theories are distinct from each other in their key assumptions, parameterized processes, and, particularly, selection mechanisms for the zonal spatial scale, time scale, and eastward propagation of the MJO. The comparison of the four theories and more recent development in MJO dynamical approaches lead to a realization that theoretical thinking of the MJO is diverse and understanding of MJO dynamics needs to be further advanced. Plain Language Summary The Madden‐Julian Oscillation (MJO) is a tropical phenomenon that includes heavy rainfall and stiff wind over an area of roughly 1,500 km in latitude and 4,500 km in longitude. It starts over the Indian Ocean and moves eastward to the Pacific Ocean in about a month. As it moves eastward, it influences weather and climate phenomena in many parts of the world. Understanding the fundamental physics of the MJO forms the base for forecasting it and its global influences. This article reviews four theories of the MJO and compares their similarities and differences. Future studies needed to further our understanding of the MJO are recommended. Key Points A theory for the Madden‐Julian Oscillation (MJO) must explain its most fundamental features of temporal‐spatial scales and eastward propagation Four theories provide contrasting explanations for the MJO based on different assumptions and treatment of physical processes These MJO theories represent a general progress toward understanding the MJO and also the need to further advance such understanding