Decadal variability of the extratropical response to the Madden-Julian Oscillation

Abstract

The Madden–Julian Oscillation (MJO) is the leading mode of sub-seasonal variability in the tropical atmosphere and is a key source of predictability for extratropical weather through its teleconnection patterns. These MJO teleconnection patterns can be modulated by the El Niño-Southern Oscillation (ENSO). However, changes over decadal time scales are less well understood. ERA5 reanalysis data is used to show that the boreal winter MJO teleconnection pattern in the northern hemisphere has changed in recent decades in line with changes in the Pacific Decadal Oscillation and Atlantic Multidecadal Variability. Comparisons are made with ENSO-modulated interannual variability, showing considerable differences to the observed decadal scale variability. Changes are seen in both the circulation response and consequently in temperature and precipitation. In particular, from 1997 cold anomalies appear over Europe and the eastern United States, due to MJO convection over the western Pacific, which were not present 20 years previously.