Publication: On the Relationship between ENSO, Stratospheric Sudden Warmings, and Blocking
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2014-06-15
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American Meteorological Society
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Abstract
This paper examines the influence of El Niño–Southern Oscillation (ENSO) on different aspects of major stratospheric sudden warmings (SSWs), focusing on the precursor role of blocking events. The results reveal an ENSO modulation of the blocking precursors of SSWs. European and Atlantic blocks tend to precede SSWs during El Nino (EN), whereas eastern Pacific and Siberian blocks are the preferred precursors of SSWs during La Niña (LN) winters. This ENSO preference for different blocking precursors seems to occur through an ENSO effect on regional blocking persistence, which in turn favors the occurrence of SSWs. The regional blocking precursors of SSWs during each ENSO phase also have different impacts on the upward propagation of planetary-scale wavenumbers 1 and 2; hence, they determine ENSO differences in the wavenumber signatures of SSWs. SSWs occurring during EN are preceded by amplification of wavenumber 1, whereas LN SSWs are predominantly associated to wavenumber-2 amplification. However, there is not a strong preference for splitting or displacement SSWs during any ENSO phase. This is mainly because during EN, splitting SSWs do not show a wavenumber-2 pattern.
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© 2014 American Meteorological Society. This study was supported by the Spanish Ministry of Science and Innovation (MCINN) through the MATRES (CGL2012-34221) project, the Portuguese Science Foundation (FCT) through the ENAC (PTDC/AAC-CLI/103567/2008) project, and the EU FP7 program through the StratoClim project (Reference number 603557). We thank to R. García-Herrera and R. R. García for their comments. We want to acknowledge Olivia Martius and two additional reviewers who contributed to improvements in this manuscript.