ENSO Modulation of MJO Teleconnections to the North Atlantic and Europe.

The teleconnection from the Madden‐Julian Oscillation (MJO) provides a source of subseasonal variability and predictability to the North Atlantic‐European (NAE) region. The El Niño‐Southern Oscillation (ENSO) modulates the seasonal mean state, through which the MJO and its teleconnection pattern propagates; however, its impact on this teleconnection to the NAE region has not been investigated. Here we find a robust dependence of the teleconnections from the MJO to NAE weather regimes on the phase of ENSO. We show that the MJO to NAO+ regime tropospheric teleconnection is strongly enhanced during El Niño years, via enhanced Rossby wave activity, and suppressed during La Niña. Conversely, the MJO to NAO− regime stratospheric teleconnection is enhanced during La Niña years and suppressed during El Niño. This dependence on the background state has strong implications for subseasonal predictability, including interannual variations in subseasonal predictive skill. Plain Language Summary: The Madden‐Julian Oscillation (MJO) is the dominant source of differing weather conditions in the tropics on timescales within a season. The remote linkage (teleconnection) from the MJO to the North Atlantic‐European (NAE) region provides a source to modify or persist weather conditions and add predictive power to weather forecasts on 10‐ to 30‐day timescales. The El Niño‐Southern Oscillation (ENSO) has an influence on the seasonal climate state, through which the waves and linkages from the MJO to the NAE region travel. Here we find a robust dependence of these teleconnections from the MJO to NAE weather regime patterns on the ENSO state, such that under certain states of the MJO, certain regimes occur more than twice as often. The different sources and pathways also become clearer, with the teleconnections travelling via the troposphere and the stratosphere. This dependence on ENSO state has significant implications for predictions on 10‐ to 30‐day timescales. Key Points: There is a robust dependence of the teleconnections from the MJO to North Atlantic‐European weather regimes on the phase of ENSOThe MJO to NAO+ regime teleconnection via the troposphere is strongly enhanced during El Niño years, and suppressed during La NiñaThe MJO to NAO− regime teleconnection via the stratosphere is enhanced during La Niña years, and suppressed during El Niño [ABSTRACT FROM AUTHOR]