Atomic oxygen photometric temperature of lightning and its sub-processes with SOPAPILLA

Information on the temperature of lightning sub-processes is crucial to constrain the chemical and energetic impacts of lightning. However, the peer-reviewed literature on even the most energetic of these processes is scant. In this article, we present a method for measuring these temperatures using the Spectrally-resolved OPtical Automated Photometric Instrument at Langmuir LAb (SOPAPILLA), a near-infrared photometer array that enables a larger number of temperature measurements than previously possible. Across 23 lightning return strokes in the field of view of the instrument, the average peak temperature was 34.8 kK which was weakly correlated with the peak current as reported by a lightning location network. Additionally, in 33 subsequent return strokes reusing the same channel, the temperature of the precursor dart leader (15 kK) was only 3.5 kK cooler (on average) than the ensuing return stroke. We also recorded a close-range powerful stepped leader that displays stepwise temperature enhancements. Finally, by measuring the temperature of M-components (23.5 kK on average) we determine that a return stroke followed by continuing current managed to sustain a temperature of 20 kK for at least 10 ms, cooling slowly at a rate of 1.5 kK/ms.