Seminar: CPS/WTK Seminar
date: 2020 December 10 (Thu) 15:30-
Room: Online seminar (Zoom)
Speaker: Kaoru Sato (Professor, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo)
Title: The climatology of the Brewer-Dobson circulation and the contribution of gravity waves
Abstract: The climatology of material circulation in the stratosphere called the Brewer-Dobson circulation and the potential contribution of gravity waves (GWs) are examined for the annual mean state and each season using four reanalysis datasets. Resolved and unresolved waves in the datasets are respectively designated as Rossby waves and GWs. We devised a method for diagnostically estimating the GW contribution and applied to the reanalysis datasets. The GWs contribute to drive not only the summer hemispheric part of the winter deep branch and low-latitude part of shallow branches, as indicated by previous studies, but they also cause a higher-latitude extension of the deep circulation in all seasons except for summer. The autumn circulation is stronger and wider than that of spring in the equinoctial seasons. This asymmetry is attributable to the angular momentum transport associated with seasonal variation due to the radiative process. Plausible deficiencies of current GW parameterizations are discussed by comparing the diagnosed GW contribution with the parameterized GW forcing and assimilation increment.
Keywords: Brewer-Dobson circulation, atmospheric gravity waves, Rossby waves, climatology, gravity wave parameterization
Organizer: Yoshi-Yuki Hayashi