Roles of gravity waves in preconditioning of a stratospheric sudden warming

The modification of the mean flow to a suitable state for an SSW occurrence is called "vortex preconditioning." Recently, increasing attention has been paid to the role of gravity waves (GWs) in the preconditioning mechanism.

However, because of the limited availability of data sets covering the whole neutral atmosphere, much uncertainty still exists in the role of GWs in the preconditioning. The aim of this study is to investigate the mechanism of modification of the mean flow in the stratosphere and mesosphere before SSWs from a climatological viewpoint and elucidate the role of GWs in it. We use two state-of-the-art data sets covering the whole neutral atmosphere: a 17-year medium-resolution reanalysis data set and the output data from hindcast simulations performed with a GW-permitting general circulation model.