Predicting the Downward and Surface Influence of the February 2018 and January 2019 Sudden Stratospheric Warming Events in Subseasonal to Seasonal (S2S) Models

Jian Rao*, Chaim I. Garfinkel, Ian P. White

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

80 Scopus citations

Abstract

Using the real-time predictions from 11 models, this study analyzes the prediction of the downward propagation and surface impact of the 2018 and 2019 sudden stratospheric warmings (SSWs). These two SSWs differed both in their morphology types (2018: split; 2019: displacement followed by split) and magnitudes (the former being stronger). With a large sample size (>2,200) of multimodel ensemble forecasts, it is revealed that the strength of the SSW is more important than the vortex morphology in determining the magnitude of its downward impact, with strong SSWs more likely to propagate downward than weak SSWs. Therefore, based on the probabilistic forecasts, the observed strong SSW in February 2018 was more likely to have a downward and surface impact than the January 2019 SSW. The relationship between the 10-hPa dominant wave number and the 100-hPa polar cap height (or the Northern Annular Mode) is weak, implying that the dominant wave number might not be the primary factor determining the downward propagation of SSWs in the two analyzed cases. Hence, the high polar cap height (or negative Northern Annular Mode) response in the lower stratosphere and troposphere following the February 2018 SSW is mainly attributed to its strong intensity rather than the split morphology. Further, the 2-m temperature anomaly pattern following the January 2019 SSW is not forecasted due to its weak downward propagation, whereas the 2-m temperature in North Eurasia, Middle East, south China, and eastern United States could be forecasted for the downward propagating February 2018 SSW. However, regional rainfall anomalies are poorly forecasted (both in a deterministic and probabilistic sense) for both SSWs.

Original languageAmerican English
Article numbere2019JD031919
JournalJournal of Geophysical Research: Atmospheres
Volume125
Issue number2
DOIs
StatePublished - 27 Jan 2020

Bibliographical note

Publisher Copyright:
© 2020. The Authors.

Keywords

  • downward propagation
  • predictability
  • subseasonal to seasonal (S2S)
  • sudden stratospheric warming (SSW)

Fingerprint

Dive into the research topics of 'Predicting the Downward and Surface Influence of the February 2018 and January 2019 Sudden Stratospheric Warming Events in Subseasonal to Seasonal (S2S) Models'. Together they form a unique fingerprint.

Cite this