A research team from USTC has shed new light on the mechanisms of corona discharges at thunderstorm cloud tops, crucial for understanding atmospheric chemistry.
Their observations during a typhoon led to a novel model that explains how cloud-top discharges initiate and their impact on stratospheric greenhouse gases.
A research team from the University of Science and Technology of China (USTC), led by Professors Jiuhou Lei, Baoyou Zhu, and Associate Professor Feifan Liu, has achieved a breakthrough in understanding corona discharges—high-altitude electrical flashes that occur at the tops of thunderstorms and influence atmospheric chemistry. Published recently in Nature Communications, their findings introduce a new conceptual model that could deepen our grasp of these unique electrical events.
The Significance of Corona Discharges
Corona discharges, often manifesting as blue flashes near the tops of thunderstorms that penetrate into the stratosphere, are a key element in the transfer of energy and materials from the troposphere to the higher layers of the atmosphere. These discharges, particularly narrow bipolar events (NBEs), can influence the concentrations of greenhouse gases such as nitrogen oxides and ozone in the stratosphere, thereby impacting the Earth’s radiation balance.
Traditionally, it was believed that cloud-top discharges were caused by imbalances in cloud charge distribution triggered by conventional lightning. However, due to the observational challenges posed by cloud cover and Rayleigh scattering, the exact initiation mechanisms of these events have remained elusive, attracting significant interest from the scientific community.
Implications for Atmospheric Science
Utilizing an advanced ground-based lightning detection array, the research team observed NBEs during a typhoon on the Chinese coastline, uncovering a robust polarity competition between different NBE types at the cloud top. The findings indicate that positive NBEs occur predominantly during the convective uplift phase at the overshooting top of the cloud, whereas negative NBEs prevail during the convective downdraft phase, typically associated with cirrus plumes in the lower stratosphere. This observation led to the development of a new model suggesting that the intensity of convection modulates the altitude of charged layers within the cloud, which in turn governs the occurrence of cloud-top discharges.
These findings clarify the mechanisms of cloud-top discharges and their effects on stratospheric chemistry, setting the stage for more detailed studies on the broader role of thunderstorms in atmospheric processes.
Reference: “Polarity transitions of narrow bipolar events in thundercloud tops reaching the lower stratosphere” by Feifan Liu, Torsten Neubert, Olivier Chanrion, Gaopeng Lu, Ting Wu, Fanchao Lyu, Weitao Lyu, Christoph Köhn, Dongshuai Li, Baoyou Zhu and Jiuhou Lei, 26 August 2024, Nature Communications.
DOI: 10.1038/s41467-024-51705-y
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1 Comment
“… corona discharges—high-altitude electrical flashes that occur at the tops of thunderstorms and influence atmospheric chemistry.”
They can also occur at sea level. Look up St. Elmo’s Fire.