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American Geophysical Union, Journal of Geophysical Research: Atmospheres, 19(119), p. 11,116-11,134

DOI: 10.1002/2014jd022099

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Numerical simulation of the long-range propagation of gravity wave packets at high latitudes

Journal article published in 2014 by C. J. Heale, J. B. Snively ORCID, M. P. Hickey
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We use a 2-D, nonlinear, time dependent numerical model to simulate the propagation of wave packets under average high latitude, winter conditions. We investigate the ability of waves to propagate large horizontal distances, depending on their direction of propagation relative to the average modeled ambient winds. Wave sources were specified to represent: 1) The most common wave parameters inferred from observations of Nielsen et al. [2009] (18 km λx, 7.5 minute period) 2) waves consistent with the average phase speed observed (40 m/s) but outlying horizontal wavelength and period values (40 km λx, 17 minute period), and 3) waves which would be subject to strong ducting as suggested by Snively et al. [2013] (25 km λx, 6.7 minutes period). We find that wave energy density was sustained over large horizontal distances for waves ducted in the stratosphere. Waves traveling against winds in the upper stratosphere/lower mesosphere are more likely to be effectively ducted in the stratosphere and travel large horizontal distances, while waves which escape in the form of leakage are more likely to be freely propagating above 80 km altitude. Waves propagating principally in the direction of the stratopause winds are subject to weaker stratospheric ducting and thus increased leakage of wave energy density from the stratosphere. However, these waves are more likely to be subject to reflection and ducting at altitudes above 80 km based upon the average winds chosen. The wave periods that persist at late times in both the stratosphere and the MLT range from 6.8-8 minutes for cases 1 and 3. Shorter period waves tend to become trapped in the stratosphere, while longer period waves can dissipate in the thermosphere with little reflection or trapping. It is suggested that the most common scenario is of partial ducting, where waves are observed in the airglow after they leak out of the stratosphere, especially at large horizontal distances from the source. Stratospheric ducting and associated leakage can contribute to a periodic and horizontally distributed forcing of the MLT.