Optical pulse propagation through clouds

Matter, John C.; Bradley, Robert G.

doi:10.1364/ao.20.002220

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…If light reaches the observer through forward scattering, it will not have been delayed significantly or distorted. Matter and Bradley [] show experimentally with 10 ns laser pulses that clouds of optical depth 8 to 20, in a path length of 765 m, do not significantly delay or distort the laser pulse for observations made in the direction of the laser and 10° away from that direction. On the other hand, Bucher and Lerner [] sent laser pulses through higher optical depth clouds than Matter and Bradley [] and measured a time spreading of the laser pulse up to 10 µs observed up to 45° off axis to the laser.…”

Section: Discussionmentioning

confidence: 99%

“…Matter and Bradley [] show experimentally with 10 ns laser pulses that clouds of optical depth 8 to 20, in a path length of 765 m, do not significantly delay or distort the laser pulse for observations made in the direction of the laser and 10° away from that direction. On the other hand, Bucher and Lerner [] sent laser pulses through higher optical depth clouds than Matter and Bradley [] and measured a time spreading of the laser pulse up to 10 µs observed up to 45° off axis to the laser. Bucher and Lerner [] observed that maximum laser signal reception and the fastest received signal risetime were in the direction to the laser, but even those signals had a decaying tail attributed to multiple scattering.…”

Section: Discussionmentioning

confidence: 99%

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Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

et al. 2016

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We present simultaneously measured luminosity and electric field data from the initial breakdown (IB) stage in seven cloud-to-ground (CG) and eight intracloud (IC) lightning discharges along with, in three cases, radar and Lightning Mapping Array (LMA) data. The data were taken in north-central Florida in 2013 and 2014. Seven CG discharges had an arithmetic mean (standard deviation, SD) IB stage luminosity pulse train duration of 3 ms (2 ms), and within the seven CG discharges, 30 luminosity pulses had the following means (SD): 10% to 90% risetime 25 μs (16 μs), full width at half maximum 68 μs (21 μs), and delay between onset of the electric field pulse and associated luminosity pulse 8 μs (8 μs). Eight IC discharges had a mean (SD) IB stage luminosity pulse train duration of 11 ms (4 ms), and within the 8 IC discharges, 37 luminosity pulses exhibited mean risetimes, widths, and delays of 59 μs (36 μs), 176 μs (70 μs), and 34 μs (20 μs), all significantly greater than in the CG case. The roughly 10 LMA sources associated with each of the three IB stages in 2014 are grouped horizontally within about 1 km 2 . The mean altitude (SD) of the LMA points during two CG IB stages is 5 km (600 m) and 4.3 km (250 m) and during one IC discharge is 6.2 km (550 m). We discuss the role of optical scattering in delaying and distorting the observed luminosity waveforms.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

et al. 2016

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“…[]. In all cases herein we estimate that the photons are scattered through angles of less than 10 o as seen from the camera; based on Bucher and Lerner [] and Matter and Bradley [] the delay caused by scattering for these cases may be up to 3 µs and has not been included in T D10 . Scattering will also lengthen the overall duration of the luminosity increases, but in our cases this effect is small relative to our 20 µs time window of the video data.…”

Section: Data Sourcesmentioning

confidence: 99%

Luminosity with intracloud‐type lightning initial breakdown pulses and terrestrial gamma‐ray flash candidates

et al. 2016

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High‐speed video data for four hybrid lightning flashes show luminosity bursts at visible wavelengths that are time‐correlated with large, intracloud flash (IC) initial breakdown (IB) pulses in electric field change (E‐change) data. The candidate IC‐type IB pulses are large in range‐normalized E‐change amplitude and peak current (2.2‐3.4 V/m at 100 km, 2.9‐11.1 kA) and have slow (0.3‐2.2 ms duration) field changes corresponding to charge moment changes of 0.5‐15 C km. Such large amplitude IB pulses have been associated with production of terrestrial gamma‐ray flashes in prior work. No gamma‐ray observations were available for these events. In each flash, a luminosity increase was evident in the video data at the time of the largest IC‐type IB pulses, when VHF sources and E‐change data indicate the IC initial leader was at 6.1 ‐ 9.4 km altitude and rapidly developing upward. Luminosity starts increasing within ‐10 µs to +20 µs of the main IC‐type IB pulse peak, i.e., within the same 20‐µs video frame as that in which the E‐change peak occurs. Delay time between the beginning of the E‐change pulse and beginning of the luminosity increase is 40‐110 µs. Video intensities increase sharply for 80‐220 µs to maximum value, then decrease over a longer period, with entire burst durations of 300‐800 µs. The time lag between IB pulse peak and maximum luminosity is consistent with these IC‐type IB pulses starting a large current that peaks and becomes bright at the time of the main pulse peak, and lasts for several hundred microseconds.

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“…Guo and Krider () offered a generic sense of what the initial portion of lightning's unobscured optical emission looks like, but a single canonical estimate is unlikely representative of natural breadth, leaving us limited in our understanding of the optical “truth term” for different lightning processes. Attempts have therefore likewise been made to address the stochastic scattering process and to dredge a unique source term from propagated signals (Davis & Koshak et al, ; Light et al, ; Marshak, ; Matter & Bradley, ; Thomason & Krider, ). Statistical comparison of scattered light with models confirms that the process is one of modified diffusion and that unfortunately the consequences of the multiple scatterings are non‐unique (Light et al, ).…”

Section: General Forte Optical Findingsmentioning

confidence: 99%

A Retrospective of Findings From the FORTE Satellite Mission

Light

2020

JGR Atmospheres

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We revisit the findings from the FORTE satellite program (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004), which collected optical imaging of lightning as well as optical and radio frequency time series waveforms globally from low-earth-orbit. These include surveys of the earth's radio frequency anthropogenic noise environment; earth surface reflectivity at radio frequencies; a scheme for classifying lightning discharge types on the basis of their very high frequency time domain power envelope; insights into the polarization and radiation pattern characteristics of different lightning types, with implications for the underlying discharge processes; and estimates of cloud optical properties based on the statistics of scattered light. Most significantly, FORTE was uniquely suited to capture large samples of data from the rare discharge known as "narrow bipolar events," enabling detailed examination of their basic characteristics and confirming that they appear to result from fundamentally distinct physical processes compared to other lightning. In particular, despite representing huge charge transfer they evidently produce little-to-no light output.

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Optical pulse propagation through clouds

Cited by 10 publications

References 7 publications

Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

Luminosity in the initial breakdown stage of cloud‐to‐ground and intracloud lightning

Luminosity with intracloud‐type lightning initial breakdown pulses and terrestrial gamma‐ray flash candidates

A Retrospective of Findings From the FORTE Satellite Mission

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