@article{TEXTUAL,
      recid = {13781},
      author = {Lu, Qian and Rao, Jian and Liang, Zhuoqi and Guo, Dong and  Luo, Jingjia and Liu, Siming and Wang, Chun and Wang, Tian},
      title = {The sudden stratospheric warming in January 2021},
      journal = {Environmental Research Letters},
      address = {2021-07-28},
      number = {TEXTUAL},
      abstract = {Using the ERA5 reanalysis, sea surface temperature and sea  ice observations, and the real-time multivariate  Madden–Julian index, this study explores a sudden  stratospheric warming (SSW) in January 2021, its favorable  conditions, and the near surface impact. Wavenumbers 1 and  2 alternately contributed to the total eddy heat flux from  mid-December 2020 to late January 2021, and the wavenumber  2 during the onset period nearly split the stratospheric  polar vortex. In mid-December 2020 and during the 2021 New  Year period (1–5 January 2021), a blocking developed over  the Urals, which enhanced the local ridge and the  climatological wavenumber 2. Composite results confirm that  the Arctic sea ice loss in autumn and La Niña favor the  deepening of the high latitude North Pacific low and the  increase of the Urals height ridge, which together enhance  the planetary waves and hence disturb the stratospheric  polar vortex. However, the Madden–Julian oscillation (MJO)  in the tropics was dormant in mid-to-late December 2020 and  early January 2021, and the well-established statistical  relationship between the MJO convection over the western  Pacific and the SSW is not applicable to this special case.  The cold air outbreak in China during the 2021 New Year  period before the January 2021 SSW onset is not explained  by the SSW signal which developed in the stratosphere. In  contrast, the downward-propagating signal reached the near  surface in mid-February 2021, which may contribute to the  cold air outbreak in US and may help to explain the extreme  coldness of Texas in middle February.},
      url = {http://knowledge.uchicago.edu/record/13781},
}