Southern Hemisphere extratropical gravity wave sources and intermittency revealed by a middle-atmosphere general circulation model
journal contributionposted on 2023-05-18, 20:21 authored by Simon AlexanderSimon Alexander, Sato, K, Watanabe, S, Kawatani, Y, Damian MurphyDamian Murphy
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.
Publication titleJournal of The Atmospheric Sciences
Department/SchoolInstitute for Marine and Antarctic Studies
PublisherAmer Meteorological Soc
Place of publication45 Beacon St, Boston, USA, Ma, 02108-3693
Rights statementCopyright 2016 American Meteorological Society