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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

The lightning ground flash : an engineering study.

Eriksson, Andrew John. January 1979 (has links)
The thesis is concerned with a study of the electrical engineering parameters of the lightning ground flash - i.e. the statistical distributions of peak current amplitudes, discharge current waveform characteristics, and flash striking distances - in the event of flashes to practical engineering structures. In view of its predominating frequency of occurrence in practical situations, the discharge of primary concern is the downward progressing and negatively charged ground flash. A central feature of this work is the establishment of a lightning research station (incorporating a 60 m instrumented mast) in the Transvaal highveld region of South Africa. The design of this station and the related measurement techniques are fully described. Preliminary results accumulated over a 6-year period of observation are presented, and include recordings obtained during direct strikes to the mast, as well as data from associated measurements of additional thunderstorm and lightning parameters. The latter studies include the use of closed circuit television video recordings, together with electrostatic field mills and lightning flash counters. Analysis of the resultant data serves to provide a comprehensive characterisation of the thunderstorm and lightning climatology in the region - on the basis of electrical activity. With only few exceptions, it is concluded that the characteristics of lightning observed in the. Transvaal region are generally consistent with the trends of data from other regions of the world. A unique aspect of the project is a study of lightning striking distances. An attempt to estimate these distances using bi-directional photography of flashes to the research mast is described, and several preliminary results are also presented - in conjunction with the associated measurements of discharge current amplitude. These results are compared with previously used relationships between striking distance and peak current. / Thesis (Ph.D.)-University of Natal, Durban, 1979.
12

The Impact of Mountain Topography and Environmental Flow on the Predictability of Localized Thunderstorms / 地形と環境風が局地的な雷雨の予測可能性に及ぼす影響

Wu, Pin-Ying 25 July 2022 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第24124号 / 理博第4852号 / 新制||理||1694(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 竹見 哲也, 教授 榎本 剛, 准教授 重 尚一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
13

Dual-Doppler Derived Vorticity as a Predictor of Hail Size in Severe Thunderstorms

White, Trevor Stewart 03 February 2017 (has links)
One of the primary missions of the National Weather Service (NWS) is to use a network of more than 150 NEXRAD radar installations to monitor weather for threats to life and property. Large hail produced by severe thunderstorms is a major focus of this mission. An algorithm known as the Maximum Estimated Size of Hail (MESH) algorithm is in operational use to diagnose the presence and size of hail. This study aims to use dual-Doppler observations as well as the MESH algorithm to test the idea that storms that rotate produce larger hail. Previous studies have used polarimetric radar products to detect the presence of large hail and dual-Doppler methods have been used to study embryonic hail, but no research has tested the theory of hail and rotating storms with observational evidence. A set of 59 case studies was gathered; each included a hail report submitted by a trained weather spotter or NWS employee and complete radar observations through the depth of a storm from two radars. The radar observations were resampled to a three-dimensional Cartesian grid and a dual-Doppler analysis was run on each case study. A strong correlation (stronger even than the MESH algorithm) was found between measured vorticity and hail size, lending credence to the idea that rotating storms do indeed have a higher ceiling for hail production. However, no correlation was found between MESH error and rotation. Further research will be required to evaluate whether or not this relationship can be used to augment the MESH algorithm so as to improve its skill. / Master of Science
14

Meteorological measurements with a MWR-05XP phased array radar

Sandifer, John B. 03 1900 (has links)
Scanning strategies for research and operational applications were developed for meteorological measurements with an experimental PAR, the MWR-05XP. A tornadic storm sampling strategy was developed with a 502.26 ms volumetric update and a resolution of 1.8 Az x 2 El x 150 m range. A sampling strategy for severe thunderstorm clusters was developed with a 10 second volumetric update and a resolution of 1.8 Az x 2 El x 300 m range. An operational weather scanning strategy was developed with an 81 second volumetric update and a resolution of 1.8 Az x 2 El x 150 m range. In general, for the acquisition of weather data, single frequency phased array radars offer only a slight sampling advantage over conventional scanning radars. This research verified that for meteorological sampling with the MWR-05XP, frequency diversity, coupled with electronic elevation scanning, offers a significant sampling advantage over conventional radars. The combination of electronic beam steering and frequency diversity produces a synergistic reduction in sampling time that increases the overall volumetric update rate. This research has also shown that, based on assumptions about the MWR-05XP operating parameters, it is possible to incorporate operational weather scanning into the radar's multifunction capability.
15

Thunderstorm phobia in dogs

Wallentine, Kari D. January 1900 (has links)
Master of Science / Department of Animal Sciences and Industry / Janice C. Swanson / Canine thunderstorm phobia is a common, frustrating, and complex problem that, due to the often severe nature of the clinical signs, can lead to canine relinquishment to shelters. Although a potentially treatable disorder, existing treatment options have several limitations and variable success rates. Three survey-based studies were conducted to increase the knowledge base for canine thunderstorm phobia. The first study distributed 1445 surveys through 16 Kansas veterinary clinics to determine the prevalence and characteristics of thunderstorm phobic dogs and assess differences between affected and non-affected dogs. Of 463 dogs surveyed, 240 were thunderstorm phobic as assessed by their owners. Severe weather warning systems may play a role in thunderstorm phobia. Thunderstorm phobic dogs were more fearful when exposed to tornado sirens, both during actual storms and siren testing, indicating a possible effect of classical conditioning. No differences were noted regarding sex, breed, pedigree, or neuter status. Most affected dogs preferred to be indoors remaining near their owners. The second study distributed 1600 surveys through eight Kansas animal shelters to determine the prevalence of relinquished dogs with thunderstorm phobia. Other reasons for relinquishment were also assessed. A fear of thunder was among the least common behavioral problems leading to relinquishment in dogs. Only a quarter of owners had visited a veterinarian for assistance with behavioral problems. The third study involved the administration of dog appeasing pheromone (DAP) in a double-blind, placebo-controlled, randomized clinical trial to assess its efficacy as a sole treatment for thunderstorm phobia. Data was collected from 60 dog owners using behavioral assessment questionnaires. In dogs given the placebo, six behaviors significantly improved, with another eleven showing a numerical trend toward improvement. However, in dogs given DAP, significant improvement was seen in three of these same behaviors. Consequently, these results do not indicate the potential use of DAP for reducing fearful behaviors associated with thunderstorm phobia when compared to negative controls. Information gained from these studies allows veterinarians and behavioral researchers to better understand the extent of this behavioral disorder and hopefully stimulates future research to find new and more effective ways to treat it.
16

The influence of thunderstorm downbursts on wind turbine design

Nguyen, Hieu Huy, 1980- 14 November 2013 (has links)
The International Electrotechnical Commission (IEC) standard 61400-1 for the design of wind turbines does not explicitly address site-specific conditions associated with anomalous atmospheric events or conditions. Examples of such off-standard atmospheric conditions include thunderstorm downbursts, hurricanes, tornadoes, low-level jets, etc. This study is focused on the simulation of thunderstorm downbursts using a deterministic-stochastic hybrid model and the prediction of wind turbine loads resulting from these simulated downburst wind fields. The wind velocity field model for thunderstorm downburst simulation is first discussed; in this model, downburst winds are generated separately from non-turbulent and turbulent parts. The non-turbulent part is based on an available analytical model (with some modifications), while the turbulent part is simulated as a stochastic process using standard turbulence power spectral density functions and coherence functions. Tower and rotor loads are generated using simulation of the aeroelastic response for models of utility-scale wind turbines. The main objective is to improve our understanding from the point of view of design so that we may begin to address transient events such as thunderstorm downbursts based on the simulations carried out in this research study. The study discusses as well the role of control systems (for blade pitch and turbine yaw), of models for representing transient turbulence characteristics, and of correlated demand and loads on multiple units in turbine arrays during thunderstorm downbursts. / text
17

Meteorological analysis of the 22 June 2007 F5 tornado in Elie, Manitoba

Hobson, Justin 04 January 2012 (has links)
During the early evening of 22 June 2007, a violent tornado impacted the western edge of Elie, Manitoba. This was Canada’s first documented F5 tornado. Three primary research questions were posed: (1) What were the pre-storm environmental conditions on 22 June 2007? (2) How did the storm and associated tornado evolve? (3) How does this event compare to other major tornadic events in Canada and the U.S.? The tornado passed in close proximity to a fixed-location Environment Canada Doppler radar at Woodlands, Manitoba. This allowed for a detailed examination of local mesoscale boundaries that were present prior to and during the event. The Elie tornado was rare in the fact that it looped three times within the main track and it moved approximately 5 km during its 40 minute lifetime causing F5 damage to homes and structures when it was an estimated 50 m wide.
18

Meteorological analysis of the 22 June 2007 F5 tornado in Elie, Manitoba

Hobson, Justin 04 January 2012 (has links)
During the early evening of 22 June 2007, a violent tornado impacted the western edge of Elie, Manitoba. This was Canada’s first documented F5 tornado. Three primary research questions were posed: (1) What were the pre-storm environmental conditions on 22 June 2007? (2) How did the storm and associated tornado evolve? (3) How does this event compare to other major tornadic events in Canada and the U.S.? The tornado passed in close proximity to a fixed-location Environment Canada Doppler radar at Woodlands, Manitoba. This allowed for a detailed examination of local mesoscale boundaries that were present prior to and during the event. The Elie tornado was rare in the fact that it looped three times within the main track and it moved approximately 5 km during its 40 minute lifetime causing F5 damage to homes and structures when it was an estimated 50 m wide.
19

Developing statistical guidance for afternoon lightning activity in portions of two South Florida counties

Winarchick, Justin Marsh. Fuelberg, Henry E. January 2004 (has links)
Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Henry E. Fuelberg, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.
20

Developing statistical guidance for forecasting the amount of warm season afternoon and evening lightning in South Florida

Shafer, Phillip Edmond, Fuelberg, Henry E. January 2004 (has links)
Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Henry E. Fuelberg, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

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