Vertical propagation of information in a middle atmosphere data assimilation system by gravity-wave drag feedbacks
Ren, S., Polavarapu, S. M. and Shepherd, T. G. (2008) Vertical propagation of information in a middle atmosphere data assimilation system by gravity-wave drag feedbacks. Geophysical Research Letters, 35. L06804. ISSN 0094-8276
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To link to this item DOI: 10.1029/2007GL032699
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.