文档介绍：2052 JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUME 67
A Major Stratospheric Sudden Warming Event in January 2009
YAYOI HARADA,ATSUSHI GOTO,HIROSHI HASEGAWA, AND NORIHISA FUJIKAWA
Climate Prediction Division, Japan Meteorological Agency, Tokyo, Japan
HIROAKI NAOE
Meteorological Research Institute, Tsukuba, Japan
TOSHIHIKO HIROOKA
Department of Earth and ary Sciences, Kyushu University, Fukuoka, Japan
(Manuscript received 14 September 2009, in final form 9 December 2009)
ABSTRACT
The major stratospheric sudden warming (SSW) event of January 2009 is analyzed using the Japan Meteo-
rological Agency (JMA) Climate Data Assimilation System (JCDAS). This SSW event is characterized by the
extraordinary predominance of the ary-scale wave of zonal wavenumber 2 (wave 2). The total amount of
the upward Eliassen–Palm (EP) flux for wave 2 was the strongest since the winter of 1978/79.
It is found that the remarkable development of the upper troposphere ridge over Alaska played important roles
in the SSW in January 2009. During the first development stage, the ridge excited wave packets upward as well as
eastward over around Alaska. The eastward-propagating packets intensified a trough over eastern Siberia, which
led to the development of the ary wave over eastern Siberia during the second development stage. The
results of this study indicate that the pronounced wave-2 pattern observed in the stratosphere was brought about
by accumulative effects of rather localized propagation of wave packets from the troposphere during the course of
this SSW event rather than by the ubiquitous propagation of ary-scale disturbances in the troposphere.
The features of the SSW in January 2009 are quite similar to those during the major stratospheric warming
event in February 1989: both SSWs are characterized by the predominance of wave 2, the remarkable de-
velopment of the upper troposphere ridge over around Alaska, and positive SSTs in the eastern part of the