Abstract
This study uses Fast On-Orbit Detection of Transient Events (FORTE)
satellite observations to identify superbolt-class optical lightning
events and evaluate their origins. Superbolts have been defined by
Turman (1977) as lightning pulses whose peak optical power exceeds 1011
W. However, it has been unclear whether superbolts resulted from
particular types of high-energy lightning process or whether they were
the result of measurement bias. In the latter case, any decently-bright
lightning process could be recorded as a superbolt if the sensor had a
particularly clear sight line to the hot channel without thick clouds
diluting the optical signals. Our 12-year analysis of FORTE superbolt
detections indicates that the lower optical superbolt energy range
(~100 GW) is dominated by normal lightning, but brighter
cases are predominantly strong +CG strokes that originate from specific
types of storms. Oceanic storm systems, particularly during the winter,
and especially those located around Japan are shown to produce these
intense superbolts. We suggest that some optical superbolts result from
favorable viewing conditions and would not be identified as such by
another instrument located elsewhere, and that others are associated
with a unique set of physics that may merit the “superbolt”
distinction.