Search

Electric field measurements at Vostok station in Antarctica reveal that the El Niño—Southern Oscillation (ENSO) has a statistically significant effect on the global electric circuit, as earlier predicted by simulations. Analysis of 10 October‐February periods during 2006–2016 indicates that the shape of the diurnal variation of the surface electric field is significantly different for El Niño and La Niña years, with an especially pronounced deviation during the super El Niño of 2015/16. During strong El Niños the potential gradient relative to the diurnal mean is generally higher than usual around 8:00–14:00 UTC and lower than usual around 16:00–0:00 UTC; La Niñas are characterized by the opposite behavior. Simulations with the Weather Research and Forecasting model imply that the observed patterns are the result of changes in the global distribution of electrified clouds over the Pacific Ocean, Maritime Continent, and South America during ENSO events. Plain Language Summary: The El Niño—Southern Oscillation (ENSO) is one of the most remarkable modes of climate variability on Earth. Being made up of irregularly alternating warm (El Niño) and cold (La Niña) phases, the ENSO affects atmospheric circulation, global temperature and rainfall patterns, agriculture, and economic output. Recent simulations have suggested that changes in global convection patterns due to ENSO should also affect surface atmospheric electric fields and currents in remote regions of the planet. Here, we present electric field measurements performed during 2006–2016 at Vostok station in the Antarctic that reveal clear patterns related to ENSO as earlier predicted by simulations. Measurements show that the shape of the diurnal variation of the surface electric field is significantly different for El Niño and La Niña years (with an especially pronounced effect during the super El Niño of 2015/16), which, according to simulations, is the result of changes in the global distribution of electrified clouds over the Pacific Ocean, Maritime Continent, and South America during ENSO events. This provides further evidence of the influence of climate fluctuations on the Earth's global electromagnetic environment. Key Points: Electric field measurements in Antarctica show that strong El Niños and La Niñas consistently impact the atmospheric global circuitFor the super El Niño event of 2015/16, the anomalies in the global electric circuit are especially pronouncedSimulations show that the observed effect is due to changes in deep convection over the Pacific Ocean, Maritime Continent, and South America [ABSTRACT FROM AUTHOR]

It is known that the global electric circuit (GEC) intensity can be characterised by a single global index, namely the ionospheric potential (IP), made up of contributions from electrified clouds all over the globe. Using the Weather Research and Forecasting model, we have reproduced the atmospheric dynamics for 2008–2018 and simulated the variation of the GEC by parameterising regional contributions to the IP in terms of convection and precipitation. Considering that the El Niño—Southern Oscillation (ENSO) can be quantitatively characterised by sea surface temperatures (SSTs) in the Niño 3.4 region, this allowed us to identify and study in detail the effect of ENSO on regional contributions to the GEC. Our simulations have shown that contributions to the GEC from the land and oceanic parts of the Earth's surface respond oppositely to the ENSO cycle. The oceanic contribution is positively correlated with the Niño 3.4 SST, largely owing to increases in convection over the Pacific Ocean. In contrast to the oceans, the land contribution shows a negative correlation with ENSO due to decreases in convection over the Maritime Continent and South America. The observed correlations are statistically significant and are clearly seen on the decadal timescale; at the same time contributions to the IP for individual years do not always clearly reflect the corresponding Niño 3.4 SST anomalies. During the two El Niños and two La Niñas that occurred between 2008 and 2018, the oceanic contribution always changed in phase with ENSO, increasing in El Niño years and decreasing in La Niña years; on the other hand, the contribution of land showed a clear variation in antiphase with ENSO only for the 2015/16 El Niño and 2010/11 La Niña, characterised by extremely large SST anomalies, with a small and indefinite effect for the two lesser events. When summing the contributions of land and ocean, two strong effects of opposite signs nearly counterbalance each other and we obtain a much less pronounced effect of ENSO on the total IP. This effect is generally positive since land and ocean provide nearly equal contributions to the GEC during Northern Hemisphere winters and, according to our analysis, the contribution of ocean is slightly more sensitive to ENSO than that of land. • Simulations reveal land–ocean contrast in global electric circuit response to ENSO. • Contribution of oceans to the global circuit is positively correlated with ENSO cycle. • Contribution of land areas is, by contrast, negatively correlated with ENSO cycle. • When summing contributions over all Earth, there is a smaller positive effect of ENSO. • Key changes in convection are over the Pacific, Maritime Continent and South America. [ABSTRACT FROM AUTHOR]