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On the forcing of the Mesospheric Semi‐Annual Oscillation in the Whole Atmosphere Community Climate Model
Author(s) -
Richter Jadwiga H.,
Garcia Rolando R.
Publication year - 2006
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 - 10.1029/2005gl024378
Subject(s) - atmosphere (unit) , solstice , oscillation (cell signaling) , atmospheric sciences , advection , forcing (mathematics) , climatology , madden–julian oscillation , environmental science , gravity wave , quasi biennial oscillation , mesosphere , divergence (linguistics) , atmospheric wave , gravitational wave , physics , geology , troposphere , stratosphere , meteorology , latitude , geodesy , convection , biology , astrophysics , genetics , thermodynamics , linguistics , philosophy
The Mesospheric Semi‐Annual Oscillation in the mean zonal winds (MSAO) is a prominent feature of the tropical middle atmosphere. This oscillation is thought to be driven by the selective transmission of small‐scale gravity waves through the wind system of the stratospheric Semi‐Annual Oscillation (SSAO). However, due to limited observations, the driving mechanisms of this oscillation are not completely understood. Here we examine the driving of the MSAO using the Whole Atmosphere Community Climate Model, version 2 (WACCM2). We show that near the solstices, in addition to gravity waves, meridional advection and EP flux divergence from resolved waves (in particular from the quasi two‐day wave) contribute significantly to the momentum budget of the MSAO. Near the equinoxes, all forcing terms are weak suggesting that the easterly phase of the MSAO is driven by a process not well represented in WACCM2.