Relation between stratospheric sudden warming and the lunar effect onthe
equatorial electrojet based on Huancayo recordings
Abstract
It has been known for many decades that the lunar tidal influence in the
equatorial electrojet (EEJ) is noticeably enhanced during northern
hemisphere winters. Recent literature has discussed the role of
stratospheric sudden warming (SSW) events behind the enhancement of
lunar tides and their findings suggest a positive correlation between
the lunar tidal amplitude and lower stratospheric parameters (zonal mean
air temperature and zonal mean zonal wind) during SSW events. The
positive correlation raises the question whether an inverse approach
could also be developed which makes it possible to deduce the occurrence
of SSW events before their direct observations(before 1952) from the
amplitude of the lunar tides. This study presents an analysis technique
based on the phase of the semi-monthly lunar tide to determine the lunar
tidal modulation of the equatorial electrojet (EEJ). A statistical
approach using the superposed epoch analysis is also carried out to
formulate a relation between the EEJ tidal amplitude and lower
stratospheric parameters. Using these results, we have estimated a
threshold value for the tidal wave power that could be used to identify
years with SSW events from magnetic field observations.