FORTE Measurements of Global Optical Lightning Waveforms and Implications for Optical Lightning Detection

Geophysical Research Letters

2023

Self Cite

In the heart of the Cold War, Turman (1977) published lightning observations from the United States' Vela satellite constellation in the scientific literature. The lightning reported by Turman (1977) was not the standard collection of optical flashes that would later be used to construct the satellite lightning climatologies in use today (Albrecht et al., 2016;Christian et al., 2003;Peterson et al., 2021). Instead, Turman (1977) focused on the most powerful optical emissions generated by lightning-which they termed "superbolts." Turman (1977) found that superbolts had peak optical powers two orders of magnitude greater than ordinary lightning-radiating an estimated 10 11 -10 12 W at the source. Turman (1977) also noted that superbolts have a pattern of occurrence that differs from ordinary lightning. 9-in-10 flashes are produced by convective thunderstorms (Peterson & Liu, 2011) that arise as a consequence of atmospheric instability and local lifting mechanisms in regions with adequate moisture. Lightning "hotspots" (Albrecht et al., 2016) arise in locations where favorable conditions are frequently met. Turman's superbolts are rare (∼0.2% of all flashes) and occur in environments that are unfavorable for lightning production: mid-latitude cold-season storms with a notable hotspot in the seas surrounding Japan. This implies that superbolts are not merely the tip of the optical lightning power spectrum, but rather a rare class of discharge enabled by the unique environment.Advances in lightning detection since Turman's 1977 study are allowing us to clarify the origins of this extreme, yet incredibly rare, lightning. In 1997, the Fast On-orbit Recording of Transient Events (FORTE: Light, 2020) satellite was launched that included a photodiode detector (PDD: Kirkland et al., 2001) capable of identifying the superbolts described by Turman (1977). The Low Earth Orbit of FORTE limited its observations to thunderstorm snapshots, making it unlikely to capture a superbolt while the satellite was overhead. Still, after spending 12 years collecting data, FORTE was able to observe tens of thousands of 10 11 W events and dozens of terawatt-class superbolts.

Section: Methodsmentioning

confidence: 99%

WWLLN Energetic Lightning Events Are Different From Optical Superbolts

Geophysical Research Letters

2023

Self Cite

“…To account for potential physical and scattering delays in the optical signals (Suszcynsky et al, 2000;Peterson, 2022), we consider any event that occurs within the millisecond before the PDD trigger time to be a valid match. We only include PDD events matched with single WWLLN strokes in our analyses.…”

Section: The Forte Photodiode Detector (Pdd)mentioning

confidence: 99%

WWLLN Energetic Lightning Events are Different from Optical Superbolts

2023

Preprint

The most powerful optical emissions from lightning have been described as “superbolts” since the 1970s. In 2019, Holzworth et al. (2019) applied the superbolt label to the most energetic Radio Frequency (RF) emissions measured by the World Wide Lightning Location Network (WWLLN). In this study, we compare the WWLLN energies to optical measurements by the photodiode detector (PDD) on the Fast On-orbit Recording of Transient Events (FORTE) satellite and the Geostationary Lightning Mappers (GLMs) on NOAA’s Geostationary Operational Environmental Satellites (GOES) to assess whether WWLLN high energy events coincide with optical superbolts. We find no overlap between traditional superbolts and WWLLN high energy events. Optical superbolts are not energetic to WWLLN, while WWLLN superbolts are not optically bright. Additionally, the top WWLLN sources occur in a different meteorological context than superbolts. Despite some similarities in their overall global patterns of occurrence, WWLLN high energy events correspond to a different phenomenon.

“…Our multisensor FORTE cluster feature data is produced for the entire data record from 1997 to 2010. We used it previously to identify interesting flashes in Peterson et al (2021aPeterson et al ( , 2021b, and to generate event and flash statistics in Peterson (2022aPeterson ( , 2022c.…”

Section: Generating Cluster Feature Data For Fortementioning

confidence: 99%

FORTE Measurements of Global Lightning Altitudes

Earth and Space Science

2022

Self Cite

While multiple lightning detection systems provide geographical locations of lightning events across the globe, robust lightning altitude measurements on a global scale have proven elusive. Space‐based platforms have an advantageous viewing geometry for making these measurements, but prior studies with the Fast On‐orbit Recording of Transient Events (FORTE) satellite were limited to a few thousand events. In this study, we apply the same technique for calculating source altitude from the previous efforts to a large catalog of hundreds of thousands of global FORTE in‐cloud lightning events that were coincident with flashes geolocated by its lightning imager between 1997 and 2003. We use this new data set to document global variations in lightning altitude. As in previous studies, we find that FORTE primarily resolves sources from the upper (positive) charge layer at ∼11 km altitude in normal thunderstorms. However, sources are also recorded from other charge layers in the storm and from leaders developing between layers. In particular, we note a pronounced increase in source altitude in the first 20 ms of FORTE flashes from the negative leader developing upward into the upper positive charge layer. Regions known for wintertime and/or stratiform lightning have increased contributions from low‐altitude sources, while tropical regions particularly around Panama and the Maritime Continent have the greatest concentrations of high‐altitude sources.