Influence of the Super El Niño event during 2015/2016 on the aerosol properties and lightning activity in subtropical South America

Abstract

This work investigates the impact of ENSO on aerosols and lightning activity in subtropical South America (SSA). An analysis of the interannual variability of Aerosol Optical Depth (AOD), Ångström Exponent (AE) and different cloud parameters using MODIS satellite datasets and the lightning activity based on the lightning observations from the World Wide Lightning Location Network was performed. High positive AE, AOD anomalies and high lightning activity were found in the northeastern region of SSA during the Super El Niño event during 2015/2016 in latter spring and summer. The Pearson correlation coefficients between these aerosol parameters and monthly discharges were higher than 0.7 in the northeastern region during the Super El Niño. These positive correlations, which have been widely reported in previous studies, were explained considering the vegetation cover, consisting mainly of subtropical forests in the northeastern region of SSA, and the increase in rainfall during El Niño in this area in spring and summer. The increases in AOD and AE during latter spring and summer in the northeastern region were therefore related to the release of biological aerosols and to aerosols emission mechanisms independent of the background aerosol concentration, respectively. The increase in lightning activity was related to the role of these released aerosols as ice nuclei particles and/or as cloud condensation nuclei, affecting cloud properties and thus the lightning activity. The results reported in this work show the effect of the Super El Niño on aerosol and lightning activity and, in this way on aerosol-cloud interactions.