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  • METEOROLOGY AND CLIMATOLOGY  (6)
  • Instrumentation and Photography  (4)
  • Meteorology and Climatology; Geophysics  (2)
  • Electronics and Electrical Engineering  (1)
  • Mathematical and Computer Sciences (General)  (1)
  • 1
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    Diffusion model for lightning radiative transfer (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A one-speed Boltzmann transport theory, with diffusion approximations, is applied to study the radiative transfer properties of lightning in optically thick thunderclouds. Near-infrared (lambda = 0.7774 micrometers) photons associated with a prominent oxygen emission triplet in the lightning spectrum are considered. Transient and spatially complex lightning radiation sources are placed inside a rectangular parallelepiped thundercloud geometry and the effects of multiple scattering are studied. The cloud is assumed to be composed of a homogeneous collection of identical spherical water droplets, each droplet a nearly conservative, anisotropic scatterer. Conceptually, we treat the thundercloud like a nuclear reactor, with photons replaced by neutrons, and utilize standard one-speed neutron diffusion techniques common in nuclear reactor analyses. Valid analytic results for the intensity distribution (expanded in spherical harmonics) are obtained for regions sufficiently far from sources. Model estimates of the arrival-time delay and pulse width broadening of lightning signals radiated from within the cloud are determined and the results are in good agreement with both experimental data and previous Monte Carlo estimates. Additional model studies of this kind will be used to study the general information content of cloud top lightning radiation signatures.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D7; p. 14,361-14,371
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Aircraft electric field measurements: Calibration and ambient field retrieval (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: An aircraft locally distorts the ambient thundercloud electric field. In order to determine the field in the absence of the aircraft, an aircraft calibration is required. In this work a matrix inversion method is introduced for calibrating an aircraft equipped with four or more electric field sensors and a high-voltage corona point that is capable of charging the aircraft. An analytic, closed form solution for the estimate of a (3 x 3) aircraft calibration matrix is derived, and an absolute calibration experiment is used to improve the relative magnitudes of the elements of this matrix. To demonstrate the calibration procedure, we analyze actual calibration date derived from a Lear jet 28/29 that was equipped with five shutter-type field mill sensors (each with sensitivities of better than 1 V/m) located on the top, bottom, port, starboard, and aft positions. As a test of the calibration method, we analyze computer-simulated calibration data (derived from known aircraft and ambient fields) and explicitly determine the errors involved in deriving the variety of calibration matrices. We extend our formalism to arrive at an analytic solution for the ambient field, and again carry all errors explicitly.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; D11; p. 22,781-22,792
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Analysis of lightning field changes produced by Florida thunderstorms (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new method is introduced for inferring the charges deposited in a lightning flash. Lightning-caused field changes (delta E's) are described by a more general volume charge distribution than is defined on a large cartesian grid system centered above the measuring networks. It is shown that a linear system of equations can be used to relate delta E's at the ground to the values of charge on this grid. It is possible to apply more general physical constraints to the charge solutions, and it is possible to access the information content of the delta E data. Computer-simulated delta E inversions show that the location and symmetry of the charge retrievals are usually consistent with the known test sources.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: NASA-TM-103539 , NAS 1.15:103539
    Format: application/pdf
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  • 4
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    Global Lightning Nitrogen Oxides Production (2014)
    In:  CASI
    Details
    Publication Date: 2018-06-12
    Description: No abstract available
    Keywords: Meteorology and Climatology; Geophysics
    Type: M13-3063
    Format: application/pdf
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  • 5
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    Retrieving Storm Electric Fields from Aircrfaft Field Mill Data: Part II: Applications (2006)
    In:  Other Sources
    Details
    Publication Date: 2018-06-12
    Description: The Lagrange multiplier theory developed in Part I of this study is applied to complete a relative calibration of a Citation aircraft that is instrumented with six field mill sensors. When side constraints related to average fields are used, the Lagrange multiplier method performs well in computer simulations. For mill measurement errors of 1 V m(sup -1) and a 5 V m(sup -1) error in the mean fair-weather field function, the 3D storm electric field is retrieved to within an error of about 12%. A side constraint that involves estimating the detailed structure of the fair-weather field was also tested using computer simulations. For mill measurement errors of 1 V m(sup -l), the method retrieves the 3D storm field to within an error of about 8% if the fair-weather field estimate is typically within 1 V m(sup -1) of the true fair-weather field. Using this type of side constraint and data from fair-weather field maneuvers taken on 29 June 2001, the Citation aircraft was calibrated. Absolute calibration was completed using the pitch down method developed in Part I, and conventional analyses. The resulting calibration matrices were then used to retrieve storm electric fields during a Citation flight on 2 June 2001. The storm field results are encouraging and agree favorably in many respects with results derived from earlier (iterative) techniques of calibration.
    Keywords: Electronics and Electrical Engineering
    Type: Journal of Atmospheric and Oceanic Technology
    Format: text
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  • 6
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    Lightning Flash Energetics (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: No abstract available
    Keywords: Instrumentation and Photography
    Type: MSFC-E-DAA-TN64875
    Format: application/pdf
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  • 7
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    A linear method for analyzing lightning field changes (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A constrained, least-squares method for analyzing multiple-station measurements of lightning field changes (delta Es) is introduced. Previous methods have attempted to fit the spatial pattern of lightning delta Es using nonlinear models, such as a point charge (Q) or a point dipole (P) model. With the linear method, the delta Es are described not by models but by a general volume charge distribution that is deposited on a large (40 x 40 x 20 cu km) Cartesian grid above the measuring network. A linear system of equations is used to relate the measured delta Es to the charges that are deposited at each grid point. With this approach, the information content of the measurements can be quantified by an eigenanalysis of the covariance matrix of the linear system. Constraints can be used to reduce the infinity of possible solutions to the linear system and also to reduce systematic biases that can be introduced by the method of solution. It is shown that a Landweber iterative method, derived from the general method of steepest descent, can be used to solve the linear system and that the resulting volume charge distributions are generally consistent with computer-simulated charge sources, when these sources are over the measuring network. The Landweber iteration has also provided solutions for natural lightning events that are consistent with Q- and P-model results.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 51; 4; p. 473-488
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  • 8
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    Preliminary Design of a Lightning Optical Camera and ThundEr (LOCATE) Sensor (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The preliminary design of an optical/acoustical instrument is described for making highly accurate real-time determinations of the location of cloud-to-ground (CG) lightning. The instrument, named the Lightning Optical Camera And ThundEr (LOCATE) sensor, will also image the clear and cloud-obscured lightning channel produced from CGs and cloud flashes, and will record the transient optical waveforms produced from these discharges. The LOCATE sensor will consist of a full (360 degrees) field-of-view optical camera for obtaining CG channel image and azimuth, a sensitive thunder microphone for obtaining CG range, and a fast photodiode system for time-resolving the lightning optical waveform. The optical waveform data will be used to discriminate CGs from cloud flashes. Together, the optical azimuth and thunder range is used to locate CGs and it is anticipated that a network of LOCATE sensors would determine CG source location to well within 100 meters. All of this would be accomplished for a relatively inexpensive cost compared to present RF lightning location technologies, but of course the range detection is limited and will be quantified in the future. The LOCATE sensor technology would have practical applications for electric power utility companies, government (e.g. NASA Kennedy Space Center lightning safety and warning), golf resort lightning safety, telecommunications, and other industries.
    Keywords: Instrumentation and Photography
    Type: AGU Meeting; Dec 10, 2001 - Dec 14, 2001; San Francisco, CA; United States
    Format: text
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  • 9
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    Flash Optical Energy from the Geostationary Lightning Mapper (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Geostationary Operational Environmental Satellite - 16 (GOES-16) Geostationary Lightning Mapper (GLM) is evaluated for many months during the Post Launch Product Test (PLPT) phase in order to ensure that optimal products are available for both the operational forecasting and broader scientific research communities. An essential aspect of the PLPT phase is to obtain a benchmark of the GLM lightning optical amplitude, so that any long-term degradation in the nadir-staring GLM camera system can be realized and quantitatively assessed. This work provides a preliminary benchmark over a 60-day period using Provisionally Validated data.
    Keywords: Instrumentation and Photography
    Type: MSFC-E-DAA-TN56036 , International Conference on Atmospheric Electricity (ICAE 2018); Jun 17, 2018 - Jun 22, 2018; Nara; Japan
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  • 10
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    Analysis of lightning field changes during active Florida thunderstorms (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A computer algorithm for deriving accurate values of lightning-caused changes in cloud electric fields under active storm conditions was developed and applied to data obtained during two thunderstorms from a network of ground-based electric field mills at the NASA Kennedy Space Center and the Cape Canaveral Air Force Station. The resulting field changes were analyzed using a least-squares optimization procedure and point-charge (Q) and point-dipole (P) models. The values and the time variations of the Q-model parameters under active storm conditions were found to be similar to those reported by Maier and Krider (1986) for small storms, when the computations were carried out with the same analysis criteria and comparable biases. The parameters of the P solutions were found to vary with time within the storm interval and from storm to storm.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 1165-118
    Format: text
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