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Vertical propagation of information in a middle atmosphere data assimilation system by gravity‐wave drag feedbacks
Author(s) -
Ren Shuzhan,
Polavarapu Saroja M.,
Shepherd Theodore G.
Publication year - 2008
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 - 10.1029/2007gl032699
Subject(s) - mesosphere , gravity wave , orographic lift , atmosphere (unit) , atmospheric sciences , geology , drag , thermosphere , wave drag , atmospheric model , geophysics , stratosphere , gravitational wave , meteorology , physics , drag coefficient , ionosphere , mechanics , oceanography , precipitation , astrophysics
The mesospheric response to the 2002 Antarctic Stratospheric Sudden Warming (SSW) is analysed using the Canadian Middle Atmosphere Model Data Assimilation System (CMAM‐DAS), where it represents a vertical propagation of information from the observations into the data‐free mesosphere. The CMAM‐DAS simulates a cooling in the lowest part of the mesosphere which is accomplished by resolved motions, but which is extended to the mid‐ to upper mesosphere by the response of the model's non‐orographic gravity‐wave drag parameterization to the change in zonal winds. The basic mechanism is that elucidated by Holton consisting of a net eastward wave‐drag anomaly in the mesosphere during the SSW, although in this case there is a net upwelling in the polar mesosphere. Since the zonal‐mean mesospheric response is shown to be predictable, this demonstrates that variations in the mesospheric state can be slaved to the lower atmosphere through gravity‐wave drag.