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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Lightning location relative to storm structure in a supercell storm and a multicell storm

Relationships between lightning location and storm structure are examined for one radar volume scan in each of two mature, severe storms. One of these storms had characteristics of a supercell storm, and the other was a multicell storm. Data were analyzed from dual-Doppler radar and dual-VHF lightning-mapping systems. The distributions of VHF impulse sources were compared with radar reflectivity, vertical air velocity, and their respective gradients. In the supercell storm, lightning tended to occur along streamlines above and down-shear of the updraft and reflectivity cores; VHF impulse sources were most concentrated in reflectivities between 30 and 40 dBZ and were distributed uniformly with respect to updraft speed. In the multicell storm, on the other hand, lightning tended to coincide with the vertical reflectivity and updraft core and with the diverging streamlines near the top of the storm. The results suggest that the location of lightning in these severe storms were most directly associated with the wind field structure relative to updraft and reflectivity cores. Since the magnitude and vertical shear of the environmental wind are fundamental in determining the reflectivity and wind field structure of a storm, it is suggested that these environmental parameters are also fundamental in determining lightning location.

Ray, Peter S.↗
NASA NTRS1998

Total Lightning and Radar Storm Characteristics Associated with Severe Storms in Central Florida

This paper examines the three dimensional characteristics of lightning flashes and severe storms observed in Central Florida during 1997-1998. The lightning time history of severe and tornadic storms were captured during the on-going ground validation campaign supporting the Lightning Imaging Sensor (LIS) experiment on the Tropical Rainfall Measuring Mission (TRMM). The ground validation campaign is a collaborative experiment that began in 1997 and involves scientists at the Global Hydrology and Climate Center, MIT/Lincoln Laboratories, and the NWS Forecast Office at Melbourne, FL. Lightning signatures that may provide potential early warning of severe storms are being evaluated by the forecasters at the NWS/MLB office. Severe storms with extreme flash rates sometimes exceeding 300 per minute and accompanying rapid increases in flash rate prior to the onset of the severe weather (hall, damaging winds, tornadoes) have been reported by Hodanish et al. and Williams et al. (1998-this conference). We examine the co-evolving changes in storm structure (mass, echo top, shear, latent heat release) and kinematics associated with these extreme and rapid flash rate changes over time. The flash frequency and density are compared with the three dimensional radar reflectivity structure of the storm to help interpret the possible mechanisms producing the extreme and rapidly increasing flash rates. For two tornadic storms examined thus far, we find the burst of lightning is associated with the development of upper level rotation in the storm. In one case, the lightning burst follows the formation of a bounded weak echo region (BWER). The flash rates diminish with time as the rotation develops to the ground in conjunction with the decent of the reflectivity core. Our initial findings suggest the dramatic increase of flash rates is associated with a sudden and dramatic increase in storm updraft intensity which we hypothesize is stretching vertical vorticity as well as enhancing the development of the mixed phase region of the storm. We discuss the importance of these factors in producing both the observed extreme flash rates and the severe weather that follows in these storms and others to be presented.

Goodman, Steven J↗
NASA NTRS1984

Solar noise storms - The polarization of storm Type III and related bursts

The spectral and polarization characteristics of 19 noise storms that occurred during 1976-1982 are reported. All components of the storms - Type I bursts and continuum, storm Type III bursts, and fine structures such as reverse drift pairs - are found to have the same sense of circular polarization. While the degree of polarization p of Type I bursts and continuum is generally greater than or approximately equal to 0.5, that of storm Type III bursts is almost always less than 0.5. Two set of storm Type III bursts stand out: one with less than or approximately equal to 0.2 and another with greater than or approximately equal to 0.3. Because these sets respectively have degrees of polarization so similar to those of fundamental (F) the harmonic (H) components of non-storm F - H pairs, it is deduced that storm Type III bursts are due sometimes to fundamental plasma radiation and sometimes to harmonic. However, F - H pairs are extremely rare among storm Type III bursts.

Dulk, G. A.↗
NASA NTRS1998

Total Lightning and Radar Storm Characteristics Associated with Severe Storms in Central Florida

A number of prior studies have examined the association of lightning activity with the occurrence of severe weather and tornadoes, in particular. High flash rates are often observed in tornadic storms (Taylor, 1973; Johnson, 1980; Goodman and Knupp, 1993) but not always. Taylor found that 23% of nontornadic storms and 1% of non-severe storms had sferics rates comparable to the tornadic storms. MacGorman (1993) found that storms with mesocyclones produced more frequent intracloud (IC) lightning than cloud-to-ground (CG) lightning. MacGorman (1993) and others suggest that the lightning activity accompanying tomadic storms will be dominated by intracloud lightning-with an increase in intracloud and total flash rates as the updraft increases in depth, size, and velocity. In a recent study, Perez et al. (1998) found that CG flash rates alone are too variable to be a useful predictor of (F4, F5) tornado formation. Studies of non-tomadic storms have also shown that total lightning flash rates track the updraft, with rates increasing as the updraft intensities and decreasing rapidly with cessation of vertical growth or downburst onset (Goodman et al., 1988; Williams et al., 1989). Such relationships result from the development of mixed phase precipitation and increased hydrometer collisions that lead to the efficient separation of charge. Correlations between updraft strength and other variables such as cloud-top height, cloud water mass, and hail size have also been observed.

Goodman, Steven J.↗
NASA NTRS1985

A study of severe storm electricity via storm intercept

Storm electricity data, radar data, and visual observations were used both to present a case study for a supercell thunderstorm that occurred in the Texas Panhandle on 19 June 1980 and to search for insight into how lightning to ground might be related to storm dynamics in the updraft/downdraft couplet in supercell storms. It was observed that two-thirds of the lightning ground-strike points in the developing and maturing stages of a supercell thunderstorm occurred within the region surrounding the wall cloud (a cloud feature often characteristic of a supercell updraft) and on the southern flank of the precipitation. Electrical activity in the 19 June 1980 storm was atypical in that it was a right-mover. Lightning to ground reached a peak rate of 18/min and intracloud flashes were as frequent as 176/min in the final stages of the storm's life.

Arnold, Roy T.↗
NASA NTRS1983

Lightning activity observed in upper and lower portions of storms and its relationship to storm structure from VHF mapping and Doppler radar

Space time mapping of very high frequencies (VHF) sources reveals lightning processes for cloud to ground (CG) and for large intracloud (IC) flashes are confined to an altitude below about 10 km and closely associated with the central high reflectivity region of a storm. Another class of IC flashes was identified that produces a splattering of small sources within the main electrically active volume of a storm and also within a large divergent wind canopy at the top of a storm. There is no apparent temporal association between the small high altitude IC flashes occurring almost continuously and the large IC and CG flashes sporadically occurring in the lower portions of storms.

Taylor, W. L.↗
NASA NTRS1986

Tropical storm Flossie and the Ark Royal storm

The development of the tropical storm Flossie north of Scotland on September 16-17, 1978 from the Ark Royal storm is described. Land, marine, upper air data, satellite imagery, Seasat scatterometer (SASS) wind data, and SMMR moisture data were utilized to analyze the storms' development. The factors which contributed to the formation of the Ark Royal storm are discussed. Isobaric surface charts, isotachs and streamlines of the SASS winds, and SMMR water vapor contours are provided.

Peteherych, S.↗
NASA NTRS1991

Study of Ardmore, Oklahoma storm clouds. I - Convective storm cloud initiation and development based on the remote sensing gravity-wave-induced convection. II - Satellite infrared remote sensing and numerical simulation

The role of gravity waves is discussed with respect to the vertical velocity of convection. Specific attention is given to wave-induced convection which contributes to the fractions of formation and the development of severe convective storms. Large-amplitude gravity waves and convective instability were investigated in storm clouds above Ardmore, Oklahoma. Rapid-scan satellite imagery and radar summaries provide evidence of water-vapor condensation related to convection which is introduced by gravity waves. Gravity wave periods of 35 minutes are found to initiate weak convection, which can be intensified by gravity waves with periods of 20 minutes. The convective motion reaches a maximum about one hour before funnel clouds develop. Other mechanisms which contribute to convective motion are considered, but gravity waves are the major contributor to the initiation, formation, and development of mesoscale storm clouds. Cloud modeling based on satellite imagery and sounding data showed that by overshooting cloud tops that penetrated the tropopause, storm clouds mature; that these clouds collapse about 9 minutes before the touchdown of tornadoes; and that cloud tops collapse at a high rate about 6 minutes before tornadoes lift off.

Hung, R. J.↗
NASA NTRS2007

Ionospheric E-Region Response to Solar-Geomagnetic Storms Observed by TIMED/SABER and Application to IRI Storm-Model Development

The large thermospheric infrared radiance enhancements observed from the TIMED/SABER experiment during recent solar storms provide an exciting opportunity to study the influence of solar-geomagnetic disturbances on the upper atmosphere and ionosphere. In particular, nighttime enhancements of 4.3 um emission, due to vibrational excitation and radiative emission by NO+, provide an excellent proxy to study and analyze the response of the ionospheric E-region to auroral electron dosing and storm-time enhancements to the E-region electron density. In this paper we give a status report of on-going work on model and data analysis methodologies of deriving NO+ 4.3 um volume emission rates, a proxy for the storm-time E-region response, and the approach for deriving an empirical storm-time correction to International Reference Ionosphere (IRI) E-region NO+ and electron densities.

Mertens, Christopher J.↗
NASA NTRS2012

Solar-Storm/Lunar Atmosphere Model (SSLAM): An Overview of the Effort and Description of the Driving Storm Environment

On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact on bodies located at 1 AU. The terrestrial magnetosphere did indeed become more electrically active during the storm passage but an obvious question is the effect of such a storm on an exposed rocky body like our Moon. The solar-storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver - the solar storm and CME passage occurring from 1-4 May 1998. We present herein an expanded discussion on the solar driver during the 1-4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had> 10 times the solar wind density and had a compositional component of He++ that exceeded 20%. We also provide a very brief overview oflhe SSLAM system layout and overarching results. One primary result is that the CME driver plasma can greatly increase the exospheric content via sputtering, with total mass loss rates that approach 1 kg/s during the 2-day CME passage. By analogy, we suggest that CME-related sputtering increases might also be expected during a CME passage by a near-earth asteroid or at the Mars exobase, resulting in an enhanced loss of material.

Farrell, W. M.↗
NASA NTRS2009

High-Altitude High-Latitude Electron-Density and Magnetic-Field Enhancements Observed during Magnetic Storms - Including the Storm of 17 April 2002

In addition to the spectacular remote measurements from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite [Burch, Space Sci. Rev., 2003], the Radio Plasma Imager (RPI) on IMAGE had the capability of making accurate magnetospheric local electron-density and magnetic-field determinations in addition to obtaining remote electron-density profiles [Reinisch et al., GRL, 2001; Benson et al., JGR, 2003]. These determinations were made using interleaved passive and active modes of operation of the RPI; the former were used to produce dynamic spectra and the latter to produce plasmagrams during active sounding. The plasmagrams of particular interest in this investigation were produced during the apogee (8 RE) portion of the IMAGE orbit when the RPI often operated in a high-resolution mode (300 Hz frequency steps) designed for accurate frequency measurements of sounder-stimulated plasma resonances. Here we present examples from 2001 and 2002, when the IMAGE apogee was at high latitudes, of large increase the electron density and magnetic-field intensity (relative to quiet control conditions) during magnetic storms. During the 17 April 2002 storm, the electron density increased by about a factor of 4 and the magnetic-field intensity increased by nearly a factor of 2. During the much larger storm of 31 March 2001, the RPI data presented in Osherovich et al. [2007] indicates that the electron density increased by about a factor of 10.

Benson, Robert F.↗
NASA NTRS2017

Automated Identification of Initial Storm Electrification and End-of-Storm Electrification Using Electric Field Mill Sensors

Kennedy Space Center (KSC) operations are located in a region which experiences one of the highest lightning densities across the United States. As a result, on average, KSC loses almost 30 minutes of operational availability each day for lightning sensitive activities. KSC is investigating using existing instrumentation and automated algorithms to improve the timeliness and accuracy of lightning warnings. Additionally, the automation routines will be warning on a grid to minimize under-warnings associated with not being located in the center of the warning area and over-warnings associated with encompassing too large an area. This study discusses utilization of electric field mill data to provide improved warning times. Specifically, this paper will demonstrate improved performance of an enveloping algorithm of the electric field mill data as compared with the electric field zero crossing to identify initial storm electrification. End-of-Storm-Oscillation (EOSO) identification algorithms will also be analyzed to identify performance improvement, if any, when compared with 30 minutes after the last lightning flash.

initial storm electrification↗
NASA NTRS1973

Direct observations in the dusk hours of the characteristics of the storm-time ring current particles during the beginning of magnetic storms

The characteristic features of the initial enhancement of the storm-time ring current particles in the evening hours are consistent with flow patterns resulting from a combination of inward convection, gradient drift, and corotation which carries plasma sheet protons into low L-values near midnight and the higher energy proton component into the plasmasphere and through the evening hours. Data from four magnetic storms during the early life of Explorer 45, when the local time of apogee was in the afternoon and evening hours, show that protons with lower magnetic moments penetrate deeper into the magnetosphere until a low limit, determined by the corotation and gradient drift forces, is reached. Such particle motions produce the stable energy dependent inner boundary of the ring current protons inside the plasmapause in the dusk sector and also provide the mechanism for energy injection into the ring current region. From the analyses of the pitch angle distributions it is evident that charge exchange and wave particle interactions are not the dominant causes of this inner boundary.

Smith, P. H.↗
NASA NTRS2019

Riders on the storm: NASA InSight Lander and the 2018 Mars global dust storm

As our spacecraft hurtled through interplanetary space towards its destination, the InSight team took stock of the situation. Would this enormous dust storm still be raging when InSight arrived? What, if anything, had this storm changed in the assumptions made by InSight’s design and test engineers about Martian atmospheric conditions for descending to the surface, or generating power there? Would InSight survive and carry out her mission?

Grover, Myron R.↗
NASA NTRS1985

Solar wind variations and geomagnetic storms - A study of individual storms based on high time resolution ISEE 3 data

Two independent methods are employed to determine the relationship between the parameter epsilon and total energy dissipation rate of the magnetosphere U sub T by selecting disturbed periods from the same data d set used by Baker et al. (1983). Specifically, four storms are examined in detail, since the accuracy of estimating U sub T is significantly improved during disturbed periods. The first method assumes that U sub T = M sub A exp.2- alpha(epsilon) where M sub A is the Alfven Mach number and alpha varies with time. The second method considers a linear, time-invariant dynamic system with epsilon as input and U sub T as output. This means that U sub T = W(asterisk)epsilon where asterisk is the convolution and W is a transfer function characteristic of the system. It is found that alpha values fluctuate mainly between 0 and -0.25. The transfer function analysis indicates that W often resembles a delta-function or a narrow rectangular impulse. Both results give the same implication (namely that U sub T is approximately equal to epsilon) and thus are consistent with the view that the magnetosphere is primarily a directly driven system during disturbed periods.

Akasofu, S.-I.↗