ACPD Atmospheric Chemistry and Physics Discussions ACPD Atmos. Chem. Phys. Discuss. 1680-7375 Göttingen, Germany 10.5194/acp-2017-563 Investigation on the abnormal quasi-two day wave activities during sudden stratospheric warming period of January 2006 Gu Sheng-Yang https://orcid.org/0000-0002-2852-0089 1 2 Dou Xiankang 1 2 3 Pancheva Dora 4 CAS Key Laboratory of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei, Anhui, China Mengcheng National Geophysical Observatory, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui, China Wuhan University, Wuhan, China National Institute of Geophysics, Geodesy and Geography, BAS, Sofia, Bulgaria 25 07 2017 2017 1 37 Copyright: © 2017 Sheng-Yang Gu et al. 2017 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://acp.copernicus.org/preprints/acp-2017-563/ The full text article is available as a PDF file from https://acp.copernicus.org/preprints/acp-2017-563/acp-2017-563.pdf

The quasi-two day wave (QTDW) during austral summer period usually coincides with sudden stratospheric warming (SSW) event in the winter hemisphere, while the influences of SSW on QTDW are not totally understood. In this work, the anomalous QTDW activities during the major SSW period of January 2006 are further investigated on the basis of hourly Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) reanalysis dataset. Strong westward QTDW with zonal wave number 2 (W2) is identified besides the conventionally dominant mode of zonal wave number 3 (W3). Meanwhile, the W3 peaks with an extremely short period of ~ 42 hours. Compared with January 2005 with no evident SSW, we found that the zonal mean zonal wind in the summer mesosphere is enhanced during 2006. The enhanced summer easterly sustains critical layers for W2 and short-period W3 QTDWs with larger phase speed, which facilitate their amplification through wave-mean flow interaction. The stronger summer easterly also provides stronger barotropic/baroclinic instabilities and thus larger forcing for the amplification of QTDW. The inter-hemispheric coupling induced by strong winter stratospheric planetary wave activities during SSW period is most likely responsible for the enhancement of summer easterly. Besides, we found that the nonlinear interaction between W3 QTDW and the wave number 1 stationary planetary wave (SPW1) may also contribute to the source of W2 at middle and low latitudes in the mesosphere.

 China Postdoctoral Science Foundation 2016T90573