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Mechanisms of some tropical intraseasonal oscillations
Author(s) -
Goswami B. N.,
Goswami P.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/92gl00488
Subject(s) - westerlies , madden–julian oscillation , climatology , oscillation (cell signaling) , rossby wave , geology , kelvin wave , quasi biennial oscillation , atmospheric sciences , mode (computer interface) , convection , meteorology , physics , troposphere , biology , computer science , genetics , operating system
A underlying mechanism for two westward propagating tropical intraseasonal oscillations is discovered. Destabilization of equatorial normal modes by moist feedbacks, in particular, by evaporation‐wind feedback, is responsible for both of them. The westward propagating 4–5 day oscillation and the quasi‐biweekly oscillation result from destabilization of the mixed Rossby gravity (MRG) wave by the evaporation‐wind feedback. The frequency and scale‐selection of the the unstable MRG wave depend critically on the background mean wind. In mean easterlies (as in the Pacific and the Atlantic), it results in the 4–5 day oscillation while in mean westerlies (as in the Indian Ocean during northern summer) it results in the quasi‐biweekly mode.