A Multiband Optical‐Radio View of Lightning Return Strokes Exposes Divergent 337/777 nm Emission Dynamics

Abstract Simultaneous observations of ultraviolet (337 nm) and near‐infrared (777 nm) lightning emissions provide insight into streamer and leader processes. However, coordinated ground‐based measurements of these bands during return strokes remain scarce. We present multiband optical and broadband radio (0.1 Hz–5 MHz) observations of 11 cloud‐to‐ground flashes (0.6–4.2 km range). For first return strokes within the photometer field of view, the 337 nm peak precedes the 777 nm peak by 38 μs on average, and 45 μs for subsequent strokes. The 337 nm emission shows faster rise times (∼5 μs) than 777 nm (∼30–40 μs) and correlates more strongly with peak current ( R 2 = 0.62 vs. 0.25). Temperature estimates indicate a hotter channel at the 777 nm maximum. Our findings demonstrate that near‐UV emissions provide a sensitive ground‐based diagnostic of the lightning attachment process and may offer improved optical proxies for estimating peak current.