Is the Madden–Julian Oscillation reliably detectable in Schumann Resonances?

The Madden-Julian Oscillation (MJO) is a quasi-periodic (30-90 days) eastward-moving atmospheric mode which primarily modifies rainfall patterns in the equatorial regions from Africa to the Pacific Ocean. It has been proposed that its signature is detectable within the intensity variations of the Schumann Resonances (SR) due to changes in the location and magnitude of the major lightning centres. Using six years of induction coil data recorded at the Eskdalemuir Observatory in the UK, we investigate whether the MJO is detectable in the first three Schumann Resonances. We extract the frequency and intensity values from each resonance every 10 min, averaged to a daily value and compare them to the Realtime Multivariate MJO (RMM) index. We use Empirical Mode Decomposition (EMD) to determine if certain modes correlate between the SR and RMM curves. We find that the EMD 30 to 70 day modes of the SR and RMM index occasionally beat in-phase during the La Niña periods of the El Niño Southern Oscillation (ENSO) but not El Niño periods. However, the relationship is not wholly consistent, implying that robust and reliable detection of the MJO in SR data remains challenging.