More Frequent Sudden Stratospheric Warming Events due to a Stronger Madden–Julian Expected in a Warmer Climate: Role of Midlatitude Tropospheric Jet

Sudden Stratospheric Warming (SSW) events influence the Arctic Oscillation and mid-latitude extreme weather, and were found to be weakly relate to the Madden-Julian Oscillation (MJO) in observations. We show that in response to a stronger MJO expected in a future warmer climate, the SSW frequency may increase and even double, and explore the mechanisms behind the MJO-SSW teleconnection. This SSW response to MJO strengthening dominates the effects of other atmospheric changes in a global warming scenario. The analysis uses both a full GCM (WACCM) and a dry core atmospheric model. The mechanism is shown to involve the modification of the mid-latitude baroclinicity and stationary wave amplitude by MJO-forced planetary waves, as well as a direct transmission of MJO-forced waves to the Arctic stratosphere.