ENSO (El Niño / La Niña) in the SR records

ENSO (El Niño / La Niña) is the dominant mode of interannual climatic variability in the tropics. It changes the distribution and size of storm regions (it relocates and enlarges or shrinks the main convective centers), and because these regions are sources of SR excitation, ENSO is reflected in the resonance records too.

In the data this shows up especially in shifts of the resonance frequencies and in changes of the distance-intensity relationship (DFR, distance-frequency relationship). Sátori et al. (2024) describe how changes in frequency in the vertical component of the electric field reflect the global dynamics of lightning on various time scales; the energy from tropical sources is moreover transferred to higher geographic latitudes with a delay of several months Satori 2024. ENSO thus manifests itself in the SR not only as an instantaneous change, but also as a time-delayed, spatially redistributed signal.

We classify this link at the level of active research: the qualitative ENSO-SR connection is well documented, but the quantitative reconstruction of specific episodes depends on station coverage and calibration (see #56).