TY - JOUR
T1 - Diagnostics of a WN2-Type Major Sudden Stratospheric Warming Event in February 2018 Using a New Three-Dimensional Wave Activity Flux
AU - Harada, Yayoi
AU - Sato, Kaoru
AU - Kinoshita, Takenari
AU - Yasui, Ryosuke
AU - Hirooka, Toshihiko
AU - Naoe, Hiroaki
N1 - Funding Information:
JRA-55 data set used in this paper is publicly available on the JMA Data Dissemination System (http://jra.kishou.go.jp/JRA-55/index_en.html) and collaborative organizations (detailed information is available on the JRA-55 website). Aura MLS data set used in this paper are available on the MLS website of Jet Propulsion Laboratory/NASA (https://mls.jpl.nasa.gov/data/overview.php). This work was partly supported by JST CREST Grant number JPMJCR1663 and, JSPS KAKENHI Grant numbers JP16H04052, JP17H01159, JP18H01270, JP18H01280, and JP18K03748.
Funding Information:
JRA‐55 data set used in this paper is publicly available on the JMA Data Dissemination System (http://jra. kishou.go.jp/JRA‐55/index_en.html) and collaborative organizations (detailed information is available on the JRA‐55 website). Aura MLS data set used in this paper are available on the MLS website of Jet Propulsion Laboratory/NASA (https://mls.jpl. nasa.gov/data/overview.php). This work was partly supported by JST CREST Grant number JPMJCR1663 and, JSPS KAKENHI Grant numbers JP16H04052, JP17H01159, JP18H01270, JP18H01280, and JP18K03748.
Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.
PY - 2019/6/27
Y1 - 2019/6/27
N2 - Observational features of atmospheric fields during a zonal wave number 2-type major sudden stratospheric warming (MSSW) event in February 2018 (MSSW18) are analyzed using the Japanese 55-year Reanalysis, satellite measurements by a microwave limb sounder, and a new three-dimensional wave activity flux. MSSW18 is characterized by a clear polar vortex split, continuance of easterlies with evident double peaks, clear planetary wave propagation in the easterly region of the upper stratosphere and extraordinary upward propagation of wave number 2 planetary waves from the upper troposphere. The upward propagation peak is comparable to that during an MSSW event in January 2009 (MSSW09), although MSSW18 shows relatively modest warming, unclear disappearance of the stratopause and weak stratopause elevation compared to those during MSSW09. Further analyses reveal that wave packets propagates upward simultaneously in both the Eastern and Western Hemispheres. Those observed in the Eastern Hemisphere converge strongly at the western edge of the Aleutian High, and most of them do not propagate further into the upper stratosphere. The wave packets observed in the Western Hemisphere propagate locally into the upper stratosphere over North America despite the fact that easterlies were predominant there in the mature stage of MSSW18. Furthermore, the results of our study reveal that the regions and levels of wave packet attenuation correspond well to the areas that smaller-scale waves have weak eastward phase tilt or are in the quasi-barotropic condition during MSSW18, whereas during MSSW09 the westward phase tilts of smaller-scale waves were clearly visible in the upper stratosphere.
AB - Observational features of atmospheric fields during a zonal wave number 2-type major sudden stratospheric warming (MSSW) event in February 2018 (MSSW18) are analyzed using the Japanese 55-year Reanalysis, satellite measurements by a microwave limb sounder, and a new three-dimensional wave activity flux. MSSW18 is characterized by a clear polar vortex split, continuance of easterlies with evident double peaks, clear planetary wave propagation in the easterly region of the upper stratosphere and extraordinary upward propagation of wave number 2 planetary waves from the upper troposphere. The upward propagation peak is comparable to that during an MSSW event in January 2009 (MSSW09), although MSSW18 shows relatively modest warming, unclear disappearance of the stratopause and weak stratopause elevation compared to those during MSSW09. Further analyses reveal that wave packets propagates upward simultaneously in both the Eastern and Western Hemispheres. Those observed in the Eastern Hemisphere converge strongly at the western edge of the Aleutian High, and most of them do not propagate further into the upper stratosphere. The wave packets observed in the Western Hemisphere propagate locally into the upper stratosphere over North America despite the fact that easterlies were predominant there in the mature stage of MSSW18. Furthermore, the results of our study reveal that the regions and levels of wave packet attenuation correspond well to the areas that smaller-scale waves have weak eastward phase tilt or are in the quasi-barotropic condition during MSSW18, whereas during MSSW09 the westward phase tilts of smaller-scale waves were clearly visible in the upper stratosphere.
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U2 - 10.1029/2018JD030162
DO - 10.1029/2018JD030162
M3 - Article
AN - SCOPUS:85067475993
VL - 124
SP - 6120
EP - 6142
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 12
ER -