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Showing papers on "Thunderstorm published in 1982"


Journal ArticleDOI
TL;DR: In this paper, a horizontal roll detected in the reflectivity pattern resulting from airflow that is deflected upward by the ground, while carrying some of the smaller precipitation ahead of the main echo core of the squall line was detected.
Abstract: This paper presents the time-dependent analysis of the thunderstorm gust front with the use of Project NIMROD data. RHI cross sections of reflectivity and Doppler velocity are constructed to determine the entire vertical structure. The life cycle of the gust front is divided into four stages: (1) the formative stage; (2) the early mature stage; (3) the late mature stage; and (4) the dissipation stage. A new finding is a horizontal roll detected in the reflectivity pattern resulting from airflow that is deflected upward by the ground, while carrying some of the smaller precipitation ahead of the main echo core of the squall line. This feature is called a 'precipitation roll'. As determined from rawinsonde data, the cold air behind the gust front accounts for the observed surface pressure rise. Calculations confirm that the collision of two fluids produce a nonhydrostatic pressure at the leading edge of the outflow. The equation governing the propagation speed of a density current accurately predicts the movement of the gust front.

341 citations


Journal ArticleDOI
TL;DR: In this paper, a strong correlation exists between the fraction of positive ground strokes and the vertical wind shear in the cloud layer, which helps to ensure that an initiating positive streamer will continue down to ground rather than into the negatively charged region that would normally be located directly below it.
Abstract: Lightning charges, locations, and currents have been determined for 12 flashes from four winter storms observed on the Hokuriku coast of Japan during December 1977 through January 1978. Additional data is available from a total of eight winter storms. The heights and magnitudes of the charges in strokes-to-ground were calculated from simultaneous measurements of electric field changes made at seven stations covering an area of about 150 km2. Discharges lowering positive charge to earth often exhibit large continuing currents (>104 A) for periods up to 10 ms. One positive discharge involved a peak current value of ≃105 A and a charge that exceeded 300°C after 4 ms. Negative continuing current strokes are generally an order of magnitude smaller, ≃4×103 A, involving charges of 100°C or less. The positive lightning charges are located higher than the negative charges of the same storm, constituting a ‘normal’ bipolar system similar to the charge configuration found in summer thunderstorms. For the eight storms observed during this study, 26 out of a total of 63 strokes-to-ground were positive. A strong correlation exists between the fraction of positive ground strokes and the vertical wind shear in the cloud layer. On the basis of this study we suggest that the occurrence of positive strokes-to-ground is a consequence of the wind shear. The shear provides a horizontal displacement between the charges that helps to ensure that an initiating positive streamer will continue down to ground rather than into the negatively charged region that would normally be located directly below it. The data suggest that positive strokes-to-ground should appear at a threshold shear value in the cloud layer of about 1.5 m/s/km.

291 citations


Book ChapterDOI
TL;DR: In this paper, the authors provide an overview of the organization and structure of precipitating cloud systems, which contribute the bulk of precipitation over the Earth, and provide a detailed analysis of the mesoscale features of these systems.
Abstract: Publisher Summary This chapter provides an overview of the organization and structure of precipitating cloud systems. The emphasis is on precipitating cloud systems, which contribute the bulk of precipitation over the Earth. Most precipitation occurs in storms that are 20–2000 km in horizontal dimension. Small showers may greatly outnumber larger precipitating cloud systems, but these do not contribute significantly to total precipitation. The cloud systems considered in this chapter are all in the mesoscale size range. Precipitation occurs over the globe in three major latitude belts. The midlatitude maxima of the Northern and Southern Hemispheres are essentially mirror images of each other and are accounted for by cloud systems associated with extratropical frontal cyclones and midlatitude thunderstorms. The equatorial maximum is accounted for mainly by rainfall from tropical cloud clusters and, to some extent, by hurricanes and smaller scale convection. This chapter explains the major precipitating cloud systems of each latitude belt and extratropical cyclones and describes midlatitude convective systems, and tropical cloud systems. Information about the mesoscale features is presented. Details are also provided about air motions within the rainband, the substructure of the rainband, the precipitation-producing mechanisms, and the dynamic processes responsible for the formation of the band.

180 citations


Journal ArticleDOI
TL;DR: Lightning and surface rainfall data were presented which were obtained during summer air mass thunderstorms at the NASA Kennedy Space Center in this paper, where a computer algorithm which employed abrupt changes in the thundercloud electric fields to detect and count flashes.
Abstract: Lightning and surface rainfall data are presented which were obtained during summer air mass thunderstorms at the NASA Kennedy Space Center. Attention is given to a computer algorithm which employed abrupt changes in the thundercloud electric fields to detect and count flashes. Statistics are given for the occurrence of lightning in 79 storms during the summer seasons of 1976-1980, as well as 28 lightning storms from the summers of 1977 and 1978. The relationship between lightning and rainfall is examined in the case of two thunderstorms whose locations allow a direct comparison of measurements. It is found that when meteorological conditions favor the production of lightning, there is an almost direct proportionality between the total rain volume and the total number of flashes.

131 citations


Journal ArticleDOI
TL;DR: In this article, a critical review of the currents and the electric and magnetic fields characteristic of cloud-to-ground and intracloud lightning is presented, focusing on the more recent work in which measured waveform variation is in the microsecond and submicro-second range.
Abstract: A critical review is presented of the currents and the electric and magnetic fields characteristic of each of the salient discharge processes which make up cloud-to-ground and intracloud lightning. Emphasis is placed on the more recent work in which measured waveform variation is in the microsecond and submicro- second range, since it is this time-scale that is of primary importance in lightning/aircraft interactions. The state of the art of the modeling of lightning currents and fields is discussed in detail. A comprehensive bibliography is given of all literature relating to both lightning measurements and models.

119 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a block diagram of the joint airport weather studies program and a detailed review of the background leading to the development of the program is reviewed, including basic studies, aircraft performance, and detection and warning techniques used to develop fine scale structure of thunderstorm dynamics and kinematics in the vicinity of a major airport.
Abstract: A block diagram of the joint airport weather studies program is presented. Background leading to the development of the program is reviewed. Basic studies, aircraft performance, and detection and warning techniques used to develop fine scale structure of thunderstorm dynamics and kinematics in the vicinity of a major airport; effect of thunderstorm low level wind shear on aircraft performance; and development of real time testing of flow level wind shear detection and warning techniques and displays are described.

87 citations


Journal ArticleDOI
TL;DR: In this paper, an investigation of severe storms that occurred on 23 May 1974 in central Oklahoma reveals interesting information on the multifaceted role of thunderstorm-produced gust fronts, such as the interaction of outflow boundaries with a cold front initiate the storms studied in this report.
Abstract: An investigation of severe storms that occurred on 23 May 1974 in central Oklahoma reveals interesting information on the multifaceted role of thunderstorm-produced gust fronts. The data reveal that the interaction of outflow boundaries with a cold front initiate the storms studied in this report. Then, the gust fronts produced by these storms have important effects on their own structure and life histories. Detailed Doppler analysis show that these storms propagate discretely along their outflow boundaries despite their supercell structure. Additionally, one storm is affected by its interaction with the boundary produced by a previous storm. This interaction appears responsible for tornadogenesis.

82 citations



Journal ArticleDOI
TL;DR: In this paper, a case study for 19 June 1980 suggests that single-Doppler weather radars of modest sensitivity can map the mesoscale divergence patterns within the convective boundary layer (CBL).
Abstract: Methods of statistical regression have been applied to single-radar radial velocity fields to map certain mesoscale (20–100 km) kinematic properties (e.g., divergence) of the convective boundary layer (CBL). Several methods, previously proposed, were found to produce estimates that were biased or whose variances were too large. When wind fields are linear on the meso- or larger scale, then single-Doppler velocity accuracies allow the estimation of horizontal divergence with an accuracy of about 4 × 10−5 s−1 and a resolution of ∼30 km, which may be sufficient to sense pre-thunderstorm convergence A case study for 19 June 1980 suggests that single-Doppler weather radars of modest sensitivity can map the mesoscale divergence patterns within the cloud-free CBL. For this day, convergence zones to the northeast seem to precede cloud development by 1–2 h, and to the west precede thunderstorms by 3–4 h.

73 citations


Journal ArticleDOI
TL;DR: In this article, the authors derived an expression for the field-dependent current density under a thunderstorm during the field recovery following a lightning discharge using the quasi-static behavior of the Maxwell current density.
Abstract: Time variations observed in thunderstorm electric fields may be interpreted in terms of a total Maxwell current density, varying slowly with time in the intervals between lightning discharges, which can be used to estimate and map thunderstorms. Using the quasi-static behavior of the Maxwell current density, an expression is derived for the field-dependent current density under a thunderstorm during the field recovery following a lightning discharge. Values of air conductivity under the small storm which range from 2 to 6 x 10 to the -13th mho/m are inferred. Data are presented which indicate that the area-average Maxwell current is not usually affected by lightning, and instead varies slowly throughout the evolution of the storm. In light of this, it is suggested that cloud electrification processes probably do not depend on the cloud electric field as much as on the more slowly varying storm dynamics and meteorological structure.

68 citations


Journal ArticleDOI
TL;DR: In this article, satellite images are used to document the life cycles of Mesoscale Convective Complexes (MCCs) which occurred over the United States during the warm season months of 1981.
Abstract: Satellite images are used to document the life cycles of Mesoscale Convective Complexes (MCCs) which occurred over the United States during the warm season months of 1981. These systems were found to exhibit characteristics similar to aspects of MCCs discussed recently in the literature; however, the behavior of several of the convective systems poses questions that can only be answered through detailed studies. The systems did produce a variety of significant weather events ranging from severe thunderstorms to locally heavy rains and flooding. Information is also provided for a number of other significant mesoscale convective systems that, although they did not meet the stringent MCC definition criteria, caught the investigators' attention. This documentation should provide a useful starting point for scientists who might wish to pursue studies of mesoscale convective weather systems.

Journal ArticleDOI
TL;DR: In this article, the authors used the Arecibo Observatory 430 MHz Doppler radar to study the upper troposphere and lower stratosphere during thunderstorm activity in the afternoon hours, and they found that gravity wave oscillations in the vertical velocity above the tropopause would develop.
Abstract: During September of 1979, the Arecibo Observatory 430 MHz Doppler radar was used to study the upper troposphere and lower stratosphere during thunderstorm activity in the afternoon hours. It was found that when the clouds developed sufficiently in the vertical direction to reach the height of the tropopause, gravity-wave oscillations in the vertical velocity above the tropopause would develop. The amplitude was 2 m/s, and the period was close to 6 min.

Journal ArticleDOI
TL;DR: In this paper, the authors used an instrumented aircraft to study the convergence and cloud formation over the mountain range during weak winds and strong insolation, and found that cumulus clouds and even thunderstorms in their early stages do not significantly affect the strength of low level convergence.
Abstract: Convection and cloud formation over mountains during weak winds and strong insolation were studied using an instrumented aircraft. Previous studies in cloudless situations had shown the existence of convergence over the mountain range at low levels, and divergence aloft. The present observations indicate that cumulus clouds and even thunderstorms in their early stages do not significantly affect the strength of the low level convergence. Furthermore, net divergence was found around clouds up to at least 6 km MSL. This favors the vertical mixing model of a cumulus cloud over the lateral entrainment model. In one case, the convergent low level heat island circulation over the mountain was observed to change to an almost non-divergent, asymmetric circulation as a thunderstorm over the mountain reached maturity.

Book ChapterDOI
01 Jan 1982
TL;DR: The recent availability of doppler radar for observations of convective storms has produced convincing documentation of the importance of rotating storms and their close association with severe weather as mentioned in this paper, and although not all severe thunderstorms rotate, an operational evaluation study conducted at NOAA’s National Severe Storms Laboratory showed that most of the storms containing meso-cyclones identifiable by Doppler Radar produced either tornadoes or large hail within an hour.
Abstract: The recent availability of doppler radar for observations of convective storms has produced convincing documentation of the importance of rotating storms and their close association with severe weather. Although not all severe thunderstorms rotate, an operational evaluation study conducted at NOAA’s National Severe Storms Laboratory showed that most of the storms containing meso-cyclones identifiable by doppler radar produced either tornadoes or large hail within an hour.

Journal ArticleDOI
TL;DR: In this article, an instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico, where it ascended past net positive charge.
Abstract: An instrumented free balloon measured electric fields and field changes as it rose through a thundercloud above Langmuir Laboratory, New Mexico. The variation of the electric field with altitude implied that the cloud contained negative space charge of density -0.6 to -4 nC/cu m between 5.5 and 8.0 km MSL. The environmental temperature at these levels ranged from -5 to -20 C. The measurements imply that the areal extent of this negative charge center was significantly greater than that of the cloud's intense precipitation shafts. At altitudes greater than 8 km, the instrument ascended past net positive charge. In addition, positive space charge adjacent to the earth's surface (concentration 0.6 nC/cu m and in the lowest portion of the cloud (1.0 nC/cu m) is inferred from the measurements. Electric field changes from intracloud lightning were interpreted by using a simple model for the developing streamer of the initial phase. Thunder source reconstructions provided estimates for the orientation of lightning channels. Seven 'streamers' so analyzed propagated on the average, at 50,000 m/s and carried a current of 390 A. The mean charge dissipated during a flash was 30 C.

Journal ArticleDOI
F. Rawlins1
TL;DR: In this article, a numerical model of cumculonimbus allowing a simulation of the growth of the electric field is described, and two possibilities are considered: an inductive method, in which hail particles are polarized in the local electric field, and a non-inductive ice-ice method, where charge transfer is attributed to a difference in surface potential of the ice particles in contact.
Abstract: A numerical model of cumculonimbus allowing a simulation of the growth of the electric field is described. The cloud model is three dimensional and includes a representation of the ice phase. The charge generating mechanism is assumed to arise from the collision of rimed hail particles with smaller ice crystals. Two possibilities are considered: an inductive method, in which hail particles are polarized in the local electric field, and a non-inductive ice-ice method, where charge transfer is attributed to a difference in surface potential of the ice particles in contact. These mechanisms are compared for a test cloud displaying the rainfall characteristics of a typical, small maritime thunderstorm and their sensitivity to the assumed form of the hail size spectrum examined. A cloud of relatively small size is chosen to constitute a more severe criterion of the strength of the electrification mechanisms than is possible in large thunderstorms where weaker modes of charge transfer could also produce a lightning discharge. Hence the comparison of mechanisms presented is specifically for a small thunderstorm. The results indicate that the electric field can reach a breakdown threshold within half an hour of the appearance of precipitation with the inductive method, providing that the hail size spectrum represents relatively small particles and that the effect of multiple collisions of any ice crystal with more than one hail particle is discounted, i.e. when it is assumed that ice crystals are uncharged before impact. It is found that the non-inductive ice-ice mechanism can lead to lightning within a similar time providing that the product of ice particle concentration and charge separation per collision exceeds 7 pC per litre.

Journal ArticleDOI
TL;DR: The morphological characteristics of mean storm-scale airflow patterns of an intense quasi-steady storm formed in South Park, Colorado are described in this paper, where it was found that the stability of the storm depended on the introduction of low-level flow directed opposite to midlevel flow, and on the formation of persistent downdrafts of sufficient magnitude to sustain an active gust front.
Abstract: The morphological characteristics of mean storm-scale airflow patterns of an intense quasi-steady storm formed in South Park, Colorado are described. Vertical transport of northerly low-level momentum within the updraft imparted a significant blocking on mid-level flow with southerly momentum. The blocking affected the movement and characteristics of adjacent, less organized storms, and additional storm-environment interactions produced an organized recirculation of precipitation particles from the mid-level updraft to the low-level updraft. The steadiness of the storm is found to have depended on the introduction of low-level flow directed opposite to mid-level flow, and on the formation of persistent downdrafts of sufficient magnitude to sustain an active gust front.

Journal ArticleDOI
TL;DR: The SESAME-AVE IV (9-10 May 1979) raw-insonde data were analyzed to uncover possible triggering mechanisms for severe storms that developed over western Oklahoma and Texas as discussed by the authors.
Abstract: The SESAME-AVE IV (9–10 May 1979) rawinsonde data were analyzed to uncover possible triggering mechanisms for severe storms that developed over western Oklahoma and Texas. The high frequency of observations (at 3 h intervals) and high vertical resolution of reported data (at 25 mb intervals) at all stations permitted investigation of the diurnal variation of the planetary boundary layer on the synoptic scale. Thunderstorms developed first just ahead of a stationary front over the Texas panhandle on the afternoon of 9 May. This area was characterized by the absence of a strong inversion (or “lid”) that represented an interface between very warm and dry air aloft, and warm moist tropical air below. Apparently, mesoscale low-level ascending motion associated with frontal lifting and/or the inland sea breeze effect led to the removal of the lid. Another noteworthy feature in this storm event was the strong vertical wind shear at low and middle levels over the storm area. When combined with the development of ...

Journal ArticleDOI
TL;DR: In this paper, a 10 cm Doppler radar was used to collect data at 16 heights within two storms at vertical incidence with a 10-cm radar, where the authors examined the reflectivity, mean velocity, and doppler spectra for time series analysis for times during and after lightning discharges.
Abstract: Digital time series data at 16 heights within two storms were collected at vertical incidence with a 10-cm Doppler radar. On several occasions during data collection, lightning echoes were observed as increased reflectivity on an oscilloscope display. Simultaneously, lightning signals from nearby electric field change antennas were recorded on an analog recorder together with the radar echoes. Reflectivity, mean velocity, and Doppler spectra were examined by means of time series analysis for times during and after lightning discharges. Spectra from locations where lightning occurred show peaks, due to the motion of the lightning channel at the air speed. These peaks are considerably narrower than the ones due to precipitation. Besides indicating the vertical air velocity that can then be used to estimate hydrometeor-size distribution, the lightning spectra provide a convenient means to estimate the radar cross section of the channel. Subsequent to one discharge, we deduce that a rapid change in the orientation of hydrometeors occurred within the resolution volume.

Journal ArticleDOI
TL;DR: In this paper, the reflectivity and polarization characteristics of ice crystals as measured with a 1.8-cm radar are reported, showing cancelation ratios of 16 to 20 dB and reflectivities of 7 to 28 dBZ.
Abstract: The reflectivity and polarization characteristics of ice crystals as measured with a 1.8-cm radar are reported. Included are measurements on stratiform ice crystal clouds, showing cancelation ratios of 16 to 20 dB and reflectivities of 7 to 28 dBZ. The degree of preferred orientation was approximately 40 to 50%. Some vertical soundings in snow appear to show changes in the snow crystal form with height. Observations of the rapid changes in polarization characteristics in the upper levels of thunderstorms show some cases for which the depolarizing particles are not the same as those which are responsible for the radar backscatter.

Journal ArticleDOI
01 Aug 1982
TL;DR: In this article, a spectral study of long planetary waves indicates that major and persistent heavy rains and severe thunderstorms in China during the past 50 years were closely related to specific anomalous large-scale circulation patterns, such as blocking highs over East Asia.
Abstract: A spectral study of long planetary waves indicates that major and persistent heavy rains and severe thunderstorms in China during the past 50 years were closely related to specific anomalous large-scale circulation patterns, such as blocking highs over East Asia. As the heavy rains of Meiyu occur, such blocking develops at high latitudes, in particular over the Sea of Okhotsk and over Lake Baikal. A southward shift of the westerlies allows upper troughs to pass over the Tibetan Plateau and low pressure disturbances, generated over the plateau area, successively move along the Yangzi River valley, causing prolonged and heavy rainfall. The establishment of an upper trough over the Bay of Bengal also provides an important condition for heavy rainfall in South China. In North and Northwest China, large-scale circulation patterns responsible for heavy rainfall events are characterized by the establishment and slow regression of a high-pressure system over the Seas of Japan and Okhotsk, or by the rapid amplification of long-wave ridges into blocking ridges near the position of seasonal-mean troughs. Owing to the blocking action of these ridges, the rain-bearing synoptic systems (typhoons, upper troughs and low-level vortices) often undergo sudden changes in their tracks or tend to slow down, becoming nearly stationary, thus enhancing and prolonging the heavy rainfall events. At the same time, a well-developed low-pressure zone in the tropics and subtropics helps to establish a strong, low-level easterly wind, which often assumes the intensity of a low-level jet. This flow configuration offers a major moisture supply for heavy rains. The study also reveals that ultralong planetary waves during heavy rainfall are more stationary than under climatological mean conditions. The departures from normal of their phase angles appear to be an important factor in generating heavy rain and severe thunderstorm episodes.

Journal ArticleDOI
TL;DR: The evolution of mesoscale systems that eventually lead to the formation of large quasi-steady storm systems is investigated in this article, where morphological and turbulent structure of the quasi-steely storm is described.
Abstract: The evolution of mesoscale systems that eventually lead to the formation of large quasi-steady storm systems is investigated. The morphological and turbulent structure of the quasi-steady storm is described. Data obtained during the South Park Area Cumulus Experiment from surface meteorological stations, rawinsondes and tethered balloons, conventional and Doppler radars, powered aircraft, and satellites, indicate that on July 19, 1977, a north-south oriented line of intense convective cells formed and remained within South Park. Elevated surface heating created a region of low-level convergence, importing Pacific moisture from west of the Rockies. The mesoscale thunderstorm line formed over this convergence zone, and a single large convective cell was observed to grow on the southern end of the mesoscale line, exhibiting supercell characteristics and substantial modifications of the environmental flow.


Journal ArticleDOI
TL;DR: A description of the observations of such an incident made by a NASA pilot was presented in this paper. The incident occurred when the pilot was flying a T-38 jet aircraft at an altitude of about 40,000 feet over Amarillo in Texas.
Abstract: It is pointed out that most lightning discharges take place within clouds or between clouds and the ground. There are a few reports, however, of a much rarer form of lightning that has been observed to come out of the top of the thunderstorm cloud and extend vertically for some distance into the clear air above it. A description is presented of the observations of such an incident made by a NASA pilot. The incident occurred when the pilot was flying a T-38 jet aircraft at an altitude of about 40,000 feet over Amarillo in Texas. The pilot found himself behind an extremely fast-moving very large cold front. A large number of lightning flashes could be seen. While most of the lightning flashes were typical, approximately every 50th or 100th discharge would go from the top of a cloud vertically upwards through the clear air towards the ionosphere. Explanations for these observations are discussed.

Journal ArticleDOI
10 Jun 1982-Nature
TL;DR: In this article, a review of the application of Doppler radar to detection of storm hazards is presented, including the use of two radar units, with a Nyquist limit on the highest wind speeds that may be recorded.
Abstract: Applications of Doppler radar to detection of storm hazards are reviewed. Normal radar sweeps reveal data on reflectivity fields of rain drops, ionized lightning paths, and irregularities in humidity and temperature. Doppler radar permits identification of the targets' speed toward or away from the transmitter through interpretation of the shifts in the microwave frequency. Wind velocity fields can be characterized in three dimensions by the use of two radar units, with a Nyquist limit on the highest wind speeds that may be recorded. Comparisons with models numerically derived from Doppler radar data show substantial agreement in storm formation predictions based on information gathered before the storm. Examples are provided of tornado observations with expanded Nyquist limits, gust fronts, turbulence, lightning and storm structures. Obtaining vertical velocities from reflectivity spectra is discussed.

Journal ArticleDOI
TL;DR: In this paper, two cases of GOES digital infrared data were analyzed during the three-hour period immediately prior to the tornado touchdown times, and it was shown that the overshooting cloud top collapsed about 15 to 30 min before the hurricane touchdown.
Abstract: Two cases of GOES digital infrared data were analyzed during the three-hour period immediately prior to the tornado touchdown times. Clouds associated with tornadoes were compared to those without tornadoes using a combination of satellite infrared and rawinsonde data. On the basis of this limited data sample, it appears as if the altitude to which the overshooting cloud top penetrated above the tropopause is the factor which determines whether or not a tornado is formed. In these cases, the overshooting cloud top collapsed about 15 to 30 min before the tornado touchdown.

Journal ArticleDOI
TL;DR: In this paper, the evolution of the turbulent structure of an intense, quasi-steady thunderstorm was examined using Doppler radar estimates of turbulent kinetic energy dissipation rates (ϵ) and radial shears of raw radial velocity (ΔVr/ΔR).
Abstract: The evolution of the turbulent structure of an intense, quasi-steady thunderstorm is examined using Doppler radar estimates of turbulent kinetic energy dissipation rates (ϵ) and radial shears of raw radial velocity (ΔVr/ΔR). A comparison of turbulent patterns with mean storm airflow is made. Observations taken during the quasi-steady mature stage reveal that turbulent intensity and activity peaked at mid to upper storm levels. The primary storm updraft was nearly turbulence-free at low levels, but exhibited increasingly turbulent activity at higher levels indicating a transition from quasi-laminar flow to bubble-like flow. Comparison of ϵ and ΔVr/ΔR patterns with environmental parameters such as equivalent potential temperature and momentum suggests that buoyancy and wind shear acted together to generate turbulent eddies, some greater than 500 m in size, at middle storm levels. At mid to upper storm levels, patterns of ϵ and ΔVr/ΔR exhibited considerable spatial and temporal variability, and maxi...

Journal ArticleDOI
TL;DR: Lightning is studied relative to storm structure using a VHP space-time discharge mapping system, radar, a cloud-to-ground flash locator, acoustic reconstruction of thunder, and other instrumentation.
Abstract: Lightning is being studied relative to storm structure using a VHP space-time discharge mapping system, radar, a cloud-to-ground flash locator, acoustic reconstruction of thunder, and other instrumentation. The horizontal discharge processes within the cloud generally propagate at speeds of 10-10 m/s. We have found horizontal extents of lightning up to 90 km. In an analysis of a limited number of flashes, lightning occured in or near regions of high cyclonic shear. Positive cloud-to-ground flashes have been observed emanating from several identifiable regions of severe storms. Lightning echoes observed with 10-cm radar are generally 10-25 dB greater than the largest precipitation echo in the storm.


Journal ArticleDOI
TL;DR: In this article, a range of phenomena producing significant atmospheric wind shears, providing more details on the shears related to thunderstorm gust fronts, are discussed. But the authors focus on the detection of wind shear in the lees of mountains.
Abstract: This paper outlines a range of phenomena producing significant atmospheric wind shears, providing more details on the shears related to thunderstorm gust fronts. A case study from a wintertime Colorado front-range experiment during 1980 documents strong wind gradients that can occur in the lees of mountains. Strengths and weaknesses of some detection methods are discussed, and evaluations of both remote-sensor and in situ sensor approaches for detecting atmospheric wind shear are emphasized.