15. Stratospheric Lightning: Blue Bolts Above the Clouds
Known as stratospheric lightning, the last and maybe most mysterious type of blue lightning happens high in the Earth’s atmosphere. This covers several forms of upper-atmospheric lightning, including blue jets and giant jets that reach from thunderstorm tops into the stratosphere. Sometimes reaching heights of up to 50 km, these unusual phenomena show as vivid blue flashes or streaks flying upward from the cloud tops. The very thin and dry air at these altitudes produces the blue colour since it lets the blue wavelengths go long distances without scattering. Stratospheric lightning is scientifically important as well as aesthetically beautiful. It offers a direct electrical link between the lower and upper atmosphere, therefore possibly affecting global atmospheric chemistry and physics. To investigate these elusive events, researchers employ advanced instruments including satellite observations and fast cameras. Knowing stratospheric lightning and its blue forms helps one to better understand the electrical circuit of the Earth and its part in the system of climate.