Observations of Blue Corona Discharges in Thunderclouds

Blue electric streamer discharges in the upper reaches of thunderclouds are observed as flashes of 337.0 nm (blue) with faint or no emissions of 777.4 nm (red). Analyzing 3 years of measurements by the Atmosphere‐Space Interactions Monitor on the International Space Station, we find that their distribution in rise time falls into two categories. One with fast rise times of 30 μs or less that are relatively unaffected by cloud scattering and emanate from within ∼2 km of the cloud tops, and another with longer rise times from deeper within the clouds. 50% of cells generating shallow events are associated with overshooting tops compared to 34% of cells generating deeper events. The median Convective Available Potential Energy of the cells is ∼70% higher for the shallow events and ∼38% higher for the deeper events than for lightning cells, suggesting the discharges are favored by strongly convective environments. Plain Language Summary Corona discharges can be seen as flashes of blue light with little or no light in a red spectral line normally emitted by lightning. They are so‐called streamers and have been observed from space in the upper regions of thunderstorm clouds. In this work we present their characteristics based on 3 years of data from the Atmosphere‐Space Interactions Monitor on the International Space Station. We find two categories of discharges, one is located at the very top of the clouds and the other a few kilometers inside the clouds. We find that the discharges on average are favored by stronger convection and higher cloud tops than normal lightning. Key Points Characterization of blue corona discharges and their meteorological environment during 3 years of observations The optical pulses of the events fall into fast (≤30 μs) and slow (40 μs to 5 ms) rise times, signifying different cloud depths The discharges occur when is 38%–70% larger than for lightning cells and are associated with overshooting tops 34%–50% of the time