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.