FORTE Perspectives on the Physical Origins of Common Optical Lightning Phenomena Observed from Space

Lightning emits transient optical and VHF signals that can be measured from orbit. However, both types of signals are modified in the Earth-atmosphere system on their way to the observing satellite. Optical lightning emissions are scattered by hydrometeors in the cloud layer between the source and sensor, while VHF lightning emissions are modified by dispersion and refraction in the ionosphere. VHF ionospheric effects are well understood and can be corrected, but the interactions between the optical emissions and the inhomogeneous thundercloud medium are sufficiently complex that the signals recorded by the instrument can contain as much information about the cloud layer as they do about the flash.

The fact that the lightning flash can be sculpted by the cloud medium inhibits the creation of optical signatures for specific lightning processes - such as Cloud-to-Ground strokes. We use coincident optical and VHF measurements taken by the FORTE satellite to identify the physical processes responsible for common optical signatures observed in lightning imager data. This combined-phenomenology examination of lightning demonstrates the value of future coordination between NOAA's Geostationary Lightning Mapper (GLM) and the upcoming Space and Endo-atmospheric Nuclear detonation detection Surveillance Experimentation and Risk-reduction (SENSER) payload. These two payloads will, together, provide a geosynchronous staring view of optical and VHF lightning signals from across the Americas, similar to FORTE's thunderstorm snapshots from low Earth orbit.