Researchers at USTC discovered how convection intensity leads to corona discharges at the tops of storm clouds. A research team from the University of Science and Technology of China (USTC), led by Professors Jiuhou Lei and Baoyou Zhu and Associate Professor Feifang Liu, has made significant progress in unraveling the mechanisms that drive coronal discharges at the tops of storm clouds. : A very important phenomenon for the chemistry of the Earth.

Their findings were published in a prestigious journal Nature Communication 26 provides a new conceptual model that could transform our understanding of these high-altitude electrical discharges.

Corona discharges, often seen as blue lights at the tops of thunderstorms, play a critical role in transporting energy and materials from the troposphere to the stratosphere. These emissions, especially narrow bipolar events (NBEs), affect the Earth’s radiation balance by affecting stratospheric levels of greenhouse gases such as nitrogen oxides and ozone.

Narrow Bipolar Events (NBE) It is an intense, high-energy lightning discharge characterized by extremely short-lived electromagnetic pulses. They differ from typical lightning strikes because of their narrow time span, usually lasting only a few microseconds. NBEs occur at high altitudes during storms and are associated with strong electric fields.

NBEs are divided into two types: positive NBEs arising from the upper layer of positive storm charge and negative NBEs arising from the lower layer of negative charge. They are considered the strongest natural sources of radio waves in the Earth’s atmosphere due to their intense electric fields and high-frequency radiation.

Researchers study NBEs to better understand lightning formation, storm dynamics and atmospheric electricity.

Problems in understanding corona discharges

Scientists once believed that cloud-top discharges were the result of charge imbalance caused by ordinary lightning. However, these events were difficult to observe due to cloud cover and Rayleigh scattering, the exact triggers of these events remain unclear, and scientific interest remains.

Using an advanced ground-based lightning detection system, the research team examined NBEs during a typhoon off the coast of China. They found strong polar competition between different cloud-top NBE types. Positive NBEs mostly occurred during the cloud-top convective updraft phase, whereas negative NBEs were more common during the convective downdraft phase and were often associated with cirrus clouds in the lower stratosphere.

These observations led to a new model in which the strength of convection determines the height of charged cloud layers, which in turn controls discharges at the cloud top. This discovery improves the understanding of how cloud discharges work and their effects on stratospheric chemistry, paving the way for further research into the role of storms in atmospheric processes.