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Southern Hemisphere extratropical gravity wave activity is examined using simulations from a free-running middle-atmosphere general circulation model called Kanto that contains no gravity wave parameterizations. The total absolute gravity wave momentum flux (MF) and its intermittency, diagnosed by the Gini coefficient, are examined during January and July. The MF and intermittency results calculated from the Kanto model agree well with results from satellite limb and superpressure balloon observations. The analysis of the Kanto model simulations indicates the following results. Nonorographic gravity waves are generated in Kanto in the frontal regions of extratropical depressions and around tropopause-level jets. Regions with lower (higher) intermittency in the July midstratosphere become more (less) intermittent by the mesosphere as a result of lower-level wave removal. The gravity wave intermittency is low and nearly homogeneous throughout the SH middle atmosphere during January. This indicates that nonorographic waves dominate at this time of year, with sources including continental convection as well as oceanic depressions. Most of the zonal-mean MF at 40°–65°S in January and July is due to gravity waves located above the oceans. The zonal-mean MF at lower latitudes in both months has a larger contribution from the land regions but the fraction above the oceans remains larger.

Item Type:	Refereed Article
Keywords:	Southern Hemisphere, gravity waves, Kanto model, momentum flux
Research Division:	Earth Sciences
Research Group:	Atmospheric Sciences
Research Field:	Atmospheric Dynamics
Objective Division:	Environment
Objective Group:	Atmosphere and Weather
Objective Field:	Atmospheric Processes and Dynamics
Author:	Alexander, S (Dr Simon Alexander)
Author:	Murphy, DJ (Dr Damian Murphy)
ID Code:	109703
Year Published:	2016
Deposited By:	CRC-Antarctic Climate & Ecosystems
Deposited On:	2016-06-28
Last Modified:	2016-10-17
Downloads:	25 View Download Statistics