scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Atmospheric coupling through wave activity changes associated with recent
stratospheric sudden warming events
Hirooka Toshihiko 1 , Ichimaru Tomoko 1 , Harada Yayoi 2
1 2
Department of Earth and Planetary Sciences, Kyushu University, Climate Prediction Division,
Japan Meteorological Agency
Stratospheric sudden warmings (SSWs) are caused by enhanced planetary waves propagating
from the troposphere and are the most spectacular planetary-scale events in the wintertime
stratospheric circulation. The polar vortex is highly distorted and breaks down within a few
days and the westerly polar night jet is quickly changed to easterlies with an accompanying
large-scale warming of the circumpolar regions. In addition, poleward shifts of the polar night
jet core are often observed prior to the occurrence of SSWs; such poleward shifts are known
as the 'preconditioning' for SSWs. Thus, dramatic changes of wind and temperature fields
would occur in mid- and high-latitudes in association with SSWs, which could bring about
activity changes of gravity waves depending on selective damping effects of background
atmosphere. While quasi-planetary waves cannot propagate vertically due to the appearance
of easterly winds, gravity waves propagate vertically and their changes may influence the
MLT region. In this study, observed changes of wind and temperature fields associated with
recent SSW events are shown and possible dynamical coupling processes due to wave activity
changes are discussed.