Occurrence of elves and lightning during El Niño and la Niña

We analyzed the ISUAL-FORMOSAT2 elves, the LIS-TRMM lightning, the sea surface temperature (SST), and the El Niño southern oscillation (ENSO) indices (the Niño 3.4 Index and the Southern Oscillation Index-SOI) in the period between June 2005 and May 2010 to explore the impacts of ENSO on the occurrences of the mesospheric elves and the troposphere lightning. The standardized anomalies of the elve and the lightning occurrence densities are used to quantify the deviation of the elve and lightning occurrences during an ENSO event. The areas in the ENSO-sensitive western Pacific, central Pacific and Tahiti regions with a significant event anomaly are taken to be the impact indicators of ENSO. Also the SOI is used to examine the correlation of the temporal intensity variation between ENSO, elve and lightning. The results indicate that elve shows clear responses to ENSO with a correlation over 0.6 in the coastal and the oceanic regions. The lightning occurrence is responsive to ENSO in the oceanic regions, but shows a low correlation in the coastal regions, due the overwhelming influence of the landmass. Therefore, between elve and lightning as proximity indices of ENSO, elve has a broader applicable geographic range. However, elve is known to be the mesospheric luminous manifestations of the high-peak-current lightning, and the response of the intense lightning to ENSO would be similar to that of the elve. Hence, alternatively, the intense lightning can also be used as an indicator of ENSO.