Driving of the SAO by gravity waves as observed from satellite

摘要: Abstract. It is known that atmospheric dynamics in the tropical stratosphere have an influence on higher altitudes and latitudes as well surface weather climate. In tropics, are governed by interplay of quasi-biennial oscillation (QBO) semiannual (SAO) zonal wind. The QBO dominant lower middle stratosphere, SAO upper stratosphere/lower mesosphere. For both driving waves plays important role. particular, role gravity still not understood. our study we use observations High Resolution Dynamics Limb Sounder (HIRDLS) satellite instrument to derive wave momentum fluxes drag order investigate interaction with SAO. These compared ERA-Interim reanalysis. Usually, westward winds much stronger than eastward winds. Therefore, mainly westward-directed phase speeds filtered out through critical-level filtering already below stratopause region. Accordingly, HIRDLS show contribute budget during wind shear, shear. findings confirm theoretical expectations qualitatively good agreement other modeling studies. most due planetary waves, likely extratropical origin. Still, find sometimes westward-propagating may Four characteristic cases background conditions identified. forcings these discussed detail, supported spectra observed HIRDLS. forcing cannot be explained alone; saturation without critical levels being reached also important.