A Coherent Image of Teleconnections Across the Globe Associated with the Madden-Julian Oscillation

The Madden-Julian Oscillation (MJO) teleconnects across the globe. These teleconnections occur on a broad range of scales, including the generation of Rossby waves in mid-latitudes and the modulation of monsoonal disturbances. Historically, various methods have been used to analyze these teleconnections, including simple one-point correlations and more complicated statistical techniques such as empirical orthogonal function (EOF) analysis. While numerous methods have proven robust for analyzing regional teleconnections, it is uncommon to be able to simultaneously identify teleconnections across the entire globe.

A statistical method was used to identify regions within the troposphere and lower stratosphere that may teleconnect with the MJO. The coherence, or magnitude-squared coherence, between the Outgoing Longwave Radiation MJO Index (OMI) and time-series of atmospheric variables was used as a proxy for the existence of teleconnections. This method permits a consistent, simultaneous analysis of such linkages across the entire globe.

Atmospheric state variables such as temperature, moisture, the zonal and meridional wind components, and geopotential height were analyzed for teleconnection patterns across the globe. Once the coherence between OMI and the atmospheric variables was calculated, regions of elevated coherence were analyzed for physical consistency. For example, the collocation of zonal and meridional wind teleconnections with geopotential teleconnections in mid-latitudes is suggestive of a barotropic wave response. The phase difference between the OMI and variable time series was also calculated to provide information about lead-lag relationships. Finally, the dependence of the coherence teleconnections on the phase of the Quasi-Biennial Oscillation (QBO) was tested by separating the analysis into periods during which the QBO was in a positive or negative phase.