Modulation by ENSO of the Relationship Between Stratospheric Sudden Warming and the Madden‐Julian Oscillation

Abstract

AbstractThe ENSO modulation on the relationship between the Madden‐Julian Oscillation (MJO) and major stratospheric sudden warming (SSW) in the Northern Hemisphere winter is analyzed. The results indicate that the statistical relationship between the MJO and SSWs is robust during La Niña years but almost nonexistent during El Niño years. During La Niña years, a significant response of stratospheric temperature appears after certain MJO phases with a distribution consistent with MJO periodicity, whereas the response becomes nonsignificant during El Niño years. Further analysis indicates that ENSO influences the MJO‐related geopotential height anomalies in middle to high latitudes of the upper troposphere, which leads to an increase in wavenumber 2 in La Niña winters. And wavenumber 2 plays a key role in generating the strong heat flux anomalies in the stratosphere. The results may help to explain the more frequent occurrence of extreme events in the stratosphere, such as SSW during La Niña winters.