The Seasonality of Madden-Julian Oscillation (MJO) Teleconnections

The Madden-Julian Oscillation (MJO) is a tropical intraseasonal phenomenon that is known to generate teleconnections like the Pacific North American and the North Atlantic Oscillation patterns in boreal winter, but knowledge about MJO teleconnections is limited during other seasons. To improve the subseasonal-to-seasonal (S2S) predictions during all seasons, this research demonstrates the strong seasonal variability of MJO teleconnections and investigates the causes of this seasonality using reanalysis and satellite data. We find that, while the MJO is strongly tied to some leading modes of the extratropics in winter, the MJO has weak relationships to the extratropical leading modes in other seasons, limiting the usability of the MJO as an S2S prediction tool. This seasonal variability in the strength and location of MJO teleconnection is strongly related to the Rossby Wave Source (RWS) generated by the MJO, determined by the seasonal location of the subtropical jet and the strength of the MJO. While the seasonal background state is often thought to play an important role, this work finds that the seasonal state of the MJO has a greater impact on determining the observed seasonal RWS patterns. This study offers an understanding that improving the prediction of the MJO seasonality would have a greater impact on improving its teleconnection than fixing the extratropical background state. Our current research indicates that the usability of the MJO as an S2S prediction tool in other seasons may depend on finding “windows of opportunities” that strengthen the ability of the MJO to form teleconnection patterns, such as other sources of interannual variability.