Interannual variability of the gravity wave drag – vertical coupling
and possible climate links
Abstract. Gravity wave drag (GWD) is an important driver of the middle atmospheric dynamics. However, there are almost no observational constraints on its strength and distribution (especially horizontal). In this study we analyze orographic GWD (OGWD) output from Canadian Middle Atmosphere Model simulation with specified dynamics (CMAM-sd) to illustrate an interannual variability of the OGWD distribution at particular pressure levels in the stratosphere and its relation to major climate oscillations. We have found significant changes of the OGWD distribution and strength depending on the phase of the North Atlantic oscillation (NAO), Quasi Biennial oscillation (QBO) and El Niño-Southern oscillation (ENSO). The OGWD variability is shown to be induced by lower tropospheric behavior by a large part. We argue that the orographic gravity waves (OGWs) and GWs in general can be a quick mediator of the tropospheric variability into the stratosphere as they have a modified impact on the stratospheric dynamics during different phases of the studied climate oscillations due to the differences in the OGWD distribution.