A Composite Assessment of Sensitivities in the Extratropical Circulation to the Madden-Julian Oscillation and Tropical Cyclones

The Madden-Julian oscillation (MJO), a large-scale coupling of tropical convection and global atmospheric circulation, is known to force atmospheric Rossby wave responses that modulate circulation patterns and contribute to the organization of extreme temperature and precipitation events across the world. Tropical cyclones (TCs) have also been shown to modulate the extratropical circulation following recurvature, thus contributing to the organization of extreme weather events. Although associations between each mode of tropical variability and the extratropical circulation have undergone extensive analysis, little work has been done to assess the range of possible circulation outcomes associated with each individual mode, and a combination of the two modes.

Lagged composites of extratropical circulation patterns associated with the MJO and active TCs at various locations are presented to demonstrate sensitivities in the extratropical circulation to the presence of these two tropical modes. Composites are stratified by days in which the MJO is considered active using the Real-time Multivariate MJO index, days in which TCs are considered active in a particular geographical region, and days in which the MJO and TCs are considered simultaneously active. Composite field significance is also assessed to demonstrate statistically significant pattern differences between each set of composites.