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1
Gallagher, Frank Woolsey. "Green thunderstorms /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1997.
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Murphy, Martin Joseph 1970. "The electrification of Florida thunderstorms." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290670.
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Six thunderstorms that occurred at the NASA Kennedy Space Center, Florida, have been studied in an attempt to characterize their electrical structure and electrification. Ground-based measurements of the cloud electric fields, the locations of lightning VHF radio sources, cloud-to-ground lightning strike points, and dual-polarization radar data were used in this study. Changes in the electric field due to lightning were used to determine the locations and magnitudes of changes in cloud charge. The fields themselves were used to compute displacement current densities following lightning flashes. The altitudes of negative charge regions were between 6.5 and 8.5 km and were almost constant. The altitude of upper positive charge exhibited more variability, and usually increased as cells developed. Amounts of charge removed by lightning increased during each cell in large storms but were nearly constant during the early part of small storms. A lower positive charge center (LPCC) usually appeared in the fields before any other charge regions could be detected at the ground. A LPCC appeared to be involved in the initiation of the majority of CG flashes. During periods of lightning, a LPCC was sometimes created by a flash, but more typically, LPCCs were produced by a cloud charge separation process. Displacement current densities were used to estimate charge accumulation rates in the cloud. The rates derived for the main negative and upper positive charge regions were compared to the average rate of charge removal by lightning. The generation rates and average lightning currents each had values ranging from 0.2 to 1.5 A and were approximately equal within expected errors in single-cell storms. Once the storm was multicellular, however, the lightning current was larger than the cloud charging rate, possibly because lightning was removing residual charge from older cells. The cloud charging rates and average lightning currents were compared with the currents computed using a non-inductive ice-graupel charging mechanism and radar-derived cloud microphysical data. This mechanism provided currents that were comparable to the observed charging rates and lightning currents and appeared to be capable of producing the LPCC.
3
Geis, Chad E. "Climate and weather analysis of Afghanistan thunderstorms." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5595.
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Approved for public release; distribution is unlimited.Thunderstorms are a significant factor in the planning and execution of Defense (DoD) operations in Afghanistan, especially in the spring and summer. Skillful forecasting of Afghanistan thunderstorms has proven difficult, even at relatively short lead times of 24 hours or less. This has led to adverse effects on a wide range of DoD missions. One potential reason for the forecasting difficulties is a lack of understanding of the conditions that lead to static instability and thunderstorms in the elevated desert mountain environment that characterizes much of Afghanistan. Much of the thunderstorm forecasting for Afghanistan is based on forecasting methods developed for the contiguous U.S. (CONUS)--for example, the use of CONUS-based static stability indices as indicators of the potential for thunderstorm development. We have investigated methods for improving thunderstorm forecasting in and near Kabul, Afghanistan, by: (1) analyzing interannual to hourly variations in thunderstorm activity; and (2) analyzing the large-scale conditions that are favorable and unfavorable for thunderstorms. We used in situ surface and radiosonde data to characterize the local conditions associated with thunderstorm variations. Our focus was on March-May, the period with the most thunderstorm activity in Kabul. We also used global reanalysis data to analyze the large-scale conditions that are favorable and unfavorable for thunderstorm development. We developed and tested two new static stability indices for use in Kabul. We also developed a large-scale circulation index to describe the regional factors that contribute to thunderstorm variations. Finally, we identified outgoing longwave radiation anomalies that occurred in specific tropical ocean basins as potential precursors for predicting thunderstorm and nonthunderstorm events at lead times of 5-15 days.
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Thornhill, Kenneth L. II. "An investigation of the environment surrounding supercell thunderstorms using wind profiler data." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/26958.
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Miller, Paul Wesley. "The Utility of Total Lightning in Diagnosing Single-cell Thunderstorm Severity in the Central Appalachian Mountains Region." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/56976.
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Recent severe weather research has examined the potential role of total lightning patterns in the severe thunderstorm warning-decision process although none to-date have examined these patterns in explicitly weak-shear environments. Total lightning flashes detected by the Earth Networks Total Lightning Network (ENTLN) during the 2012-13 convective seasons (1 May – 31 August) over a region of the Central Appalachian Mountains were clustered into likely discrete thunderstorms and subsequently classified as either single-cell or multicell/supercell storm modes. The classification of storms was determined using a storm index (SI) which was informed by current National Weather Service (NWS) identification techniques. The 36 days meeting the minimum threshold of lightning activity were divided into 24 lightning-defined (LD) single-cell thunderstorm days and 12 LD multicell/supercell days. LD single-cell days possessed statistically significant lower 0000 UTC 0-6 km wind shear (13.8 knots) than LD multicell/supercell days (26.5 knots) consistent with traditional expectations of single-cell and multicell/supercell environments respectively.
The popular 2σ total lightning jump algorithm was applied to all flashes associated with 470 individual LD thunderstorms. The frequencies of the storms’ total lightning jumps were then compared against any associated severe weather reports as an accuracy assessment. The overall performance of the algorithm among both categories was much poorer than in previous studies. While probability of detections (POD) of the 2σ algorithm were comparable to previous research, false alarm rates (FAR) were much greater than previously documented. Given these results, the 2σ algorithm does not appear fit for operational use in a weak shear environment.Master of Science
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Kozak, Steven Alexander. "Lightning strikes in Alberta thunderstorms, climatology and case studies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0006/MQ34385.pdf.
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Bahadoran, Baghbadorani Afsoon. "VR Based Aviation Training Application for Avoiding Severe Thunderstorms." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1627514676123053.
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Koshak, William John. "Analysis of lightning field changes produced by Florida thunderstorms." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185259.
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An interactive computer program .has been developed to compute accurate values of lightning-caused changes in the cloud electric field (ΔE). The ΔE' s for individual discharges in eight Florida thunderstorms have been analyzed using a nonlinear, least-squares minimization procedure and point charge (Q) and point dipole (P) models of the change in cloud charge. The results indicate that the temporal and spatial behavior of the Q- and P- model parameters are similar to those reported previously by Koshak and Krider [1989]. In all storms, the high altitude P-vectors tend to point downward toward a narrow altitude band of Q-solutions that is centered at about 8 km; low altitude P-vectors tend to point upward toward the Q-region: and the P-vectors that are at the same altitude as the Q-solutions tend to be horizontal. Because there are inherent limitations in the above least-squares analysis method and models, a new, fundamentally different approach for analyzing lightning field changes has been developed. This method finds an optimum volume charge distribution on a grid of finite dimensions and resolution. with this linear approach, we now have the ability to describe complex field change patterns subject to a variety of external constraints. We also have a framework in which a standard eigenanalysis can be used to access the general information content of data and the effects of measurement errors. Tests of the linear method with simulated lightning sources show that a centroid of the lightning charge distribution can be retrieved to within the grid resolution (2 km) when a Landweber iterative algorithm is used. Tests on three natural lightning events show that there is good agreement with previous Q- and P- model solutions and a resonable result for one event that could not be described with either a Q- or a Pmodel.
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Maggio, Christopher Ross. "Estimations of lightning charge transfers in New Mexico thunderstorms and applications to lightning energy, thunderstorm generator currents, and above-cloud transient currents /." Full text available from ProQuest UM Digital Dissertations, 2007. http://0-proquest.umi.com.umiss.lib.olemiss.edu/pqdweb?index=0&did=1609152051&SrchMode=1&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1245341216&clientId=22256.
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Knutsson, Lars. "Sprite observations over France in relation to their parent thunderstorm system." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303775.
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As a part of the European research program CAL, sprite observations were carried out from the OMP observatory in the French Pyrenees during the summer 2003. Images of the sprites were taken by two remotely controlled CCD cameras. The 23 July was considered particularly interesting because we then had access to data concerning both cloud-to-ground and intracloud lightning activity. This day was therefore chosen as the object of the present study. A large thunderstorm with two convective cores, one to the north and the other to the south, developed over the South of France during the late afternoon, and about two hours after sunset, the first sprite was detected. During a little more than three hours, 13 sprites were observed, 7 over the northern system and 6 over the southern system. The images enabled us to determine the azimuth angle of each sprite from the OMP observatory. 12 of the 13 sprites could be associated to positive cloud-to-ground flashes, and by putting together the sprite directions and the locations of the associated flashes on the radar images, we managed to get a rough idea of the position of the sprites in the storm system, and also to estimate their vertical and horizontal extent. Satellite images were included at this point of the study, and it appeared clear that sprites tend to occur over the stratiform region of the storm system in the area with the coldest (highest) cloud tops. The associated positive flashes were also within or close to this portion of the storm. The sprite occurrences were studied in relation to the cloud-to-ground and to the intracloud activity. We found that sprites seem to occur in a late stage of each storm system, when the rate of negative cloud-to-ground flashes has considerably decreased, and when the ratio of positive cloud-to-ground flashes is much higher then during the most active phase of the storm. Globally, the intracloud activity is also low during the sprite-producing periods, but sudden "bursts" of intracloud lightning could frequently be observed at the moment of the sprite. The peak current of the positive flashes was found to be rather weakly correlated to their sprite-generating capacity. The available Schumann resonance measurements seem to indicate that the charge moment is a much more adequate parameter in this respect. The areal coverage of the radar echo was calculated. The result supports the idea that sprite events tend to appear almost exclusively over large thunderstorm systems.
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Becker, Amy E. "A study of lightning flashes attending periods of banded heavy snowfall." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6036.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 11, 2008) Vita. Includes bibliographical references.
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Linder, Wolfgang. "Development of thunderstorms in Switzerland in relation to surface winds /." [S.l.] : [s.n.], 1998. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12589.
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Fennessey, Neil M. "Areal coverage of storm precipitation : observations of air mass thunderstorms." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15037.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Includes bibliographies.
by Neil Merrick Fennessey.
M.S.
14
Zea, Lina Esther Rivelli. "Thunderstorms life cycle observation: satellite multi-channel model for warning system." Instituto Nacional de Pesquisas Espaciais (INPE), 2017. http://urlib.net/sid.inpe.br/mtc-m21b/2017/07.03.18.29.
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The principal objective of this research is to identify typical cloud-top signatures of incipient thunderstorms and its early electrification process in satellite multi-channel observations as means of building a conceptual model of thunderstorm detection based on brightness temperature and electrification life cycle association. The methods toward the principal objective analyzed the data set of CHUVA-Vale field campaign from 01 November 2011 to 31 March 2012, including multi-channel observations from the SEVIRI infrared fields, a radar-lightning co-located data set and a sample of 40 compact isolated thunderstorms. The sequence for each infrared field comprises the parallax correction in satellite observations; the co-location of satellite and radar-lightning data; the selection of an evaluation area for thunderstorm detection, and the construction of brightness temperature relative cumulative-frequency distributions along with respective thresholds analysis and validation. Consequently, 4 thunderstorm predictors used in tandem to detect the largest differentiation among the lightning time steps and significant cumulus cloud and electrification intensification, resulted throughout parameters in corresponding brightness temperature histograms whose thresholds are as follows: IF1 or Predictor 1= Ch05-Ch06: (6.2 − 7.3) $\mu$m: Tbd $\geq$ −14.0 K; IF2 or Predictor 2= 10.8 $\mu$m: Tb $\leq$ +263.0 K, IF3 or Predictor 3= (6.2 − 10.8) $\mu$m: Tbd $\geq$ −14.0 K and IF4 or Predictor 4= (8.7−10.8)−(10.8−12.0) $\mu$m: Tbd $\geq$ 0 K. Additionally, an independent 2-day validation test indicated that the conceptual model has a higher probability of lightning detection for the interval of index sums from 16 to 12 because of the higher POD and lower FAR. Also the results indicated that the conceptual model has a lower probability of lightning detection for the interval of index sums from 8 to 4 because of the lower POD and higher FAR. This representative behavior of the thunderstorm electrification life cycle in geostationary satellite multi-channel observations will allow a potential development of nowcasting tools at the boundary of subtropical regions using data from the Meteosat Second Generation Satellite, and with the perspective to use in the near future, the data from the Geostationary Operational Environmental Satellite-R and the imminent Meteosat Third Generation Satellite.O objetivo principal desta pesquisa é identificar um conjunto de assinaturas típicas do topo das nuvens que permitam prever o processo de eletrificação quando as nuvens se transformam em tempestades. Através das combinações de canais dos imageadores de satélites geoestacionários este trabalho visa construir um modelo conceitual de detecção de início dos processos de eletrificação de tempestades utilizando a tendência dos histogramas de temperatura de brilho (ou diferença de canais). Para construção deste modelo conceitual foram utilizadas observações em diferentes canais infravermelhos co-localizados com observações de radar polarimétrico banda X e de medidas do LMA (Lightning Mapping Array) que consiste de fontes emitidas pelos relâmpagos em Very Higher Frequency. Foram selecionadas 40 tempestades compactas durante a campanha CHUVA-Vale para a elaboração do modelo conceitual e posteriormente os resultados foram testados em casos independentes. A sequência dos procedimentos metodológicos para campo de interesse compreende a correção da paralaxe nas observações de satélite; a co-localização com os dados de radar e descargas elétricas; a seleção de uma área de avaliação para detecção das tempestades e a construção de distribuições de frequência relativa-cumulativa de temperatura de brilho (ou diferenças) e a definição de limiares para a construção das frequências cumuladas. Quatro canais ou diferença de canais foram selecionados para detectar o processo de eletrificação da nuvem. Os seguintes preditores foram utilizados: IF1 or Predictor 1= (6.2 − 7.3) $\mu$m: Tbd $\geq$−14.0 K; IF2 or Predictor 2= 10.8 $\mu$m: Tb $\leq$+223.0 K, IF3 or Predictor 3= (6.2 − 10.8) $\mu$m: Tbd $\geq$−14.0 K and IF4 or Predictor 4= (8.7 − 10.8) − (10.8 − 12.0) $\mu$m: Tbd $\geq$ 0 K. Esse conjunto de preditores foi utilizado em função das propriedades que esses canais têm para descrever os processos microfísicos das nuvens. Após a definição do modelo, um teste de validação independente de 2 dias permitiu definir as incertezas do modelo conceitual. O emprego dos campos selecionados quando empregados juntos melhoram significativamente a previsibilidade do processo de eletrificação da nuvem. Este comportamento representativo do ciclo de vida da eletrificação das tempestades através de combinações de canais de satélite geoestacionário permitirá o desenvolvimento de ferramentas de previsão a curtíssimo prazo nas regiões tropicais e subtropicais usando dados do Meteosat Second Generation e, em breve, do Geostationary Operational Environmental Satellite-R e do futuro Meteosat Third Generation Satellite.
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McCarthy, Alexander Michael. "Convective Cores in Continental and Oceanic Thunderstorms: Strength, Width, and Dynamics." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1493652830874675.
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Marshall, Robert Andrew. "Very low frequency radio signatures of transient luminous events above thunderstorms /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Eack, Kenneth Bryan. "Observations of X rays produced by strong electric fields in thunderstorms /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1997.
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Shield, Stephen Shield. "Predictive Modeling of Thunderstorm-Related Power Outages." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu152951430854521.
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Hasa and Petrit J. "Nowcasting Hail Size for Non-Supercell Thunderstorms in the Northeastern U. S." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6805.
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Hail size prediction is a difficult task for meteorologists. The most recent method used by the United States Air Force after thunderstorm initiation involves identifying the amount of storm-top divergence and correlating that value to the height of the freezing level. However, this method was based on a study that looked at both supercell and multicell thunderstorms alike. This paper attempts to build off this previous study, although solely looking at non-supercell thunderstorms based on the hypothesis that due to dynamic differences between the storm types, common indicators found in both are not indicative that hail of similar size will be produced.
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Adang, Thomas Charles. "Structure and dynamics of the Arizona Monsoon Boundary." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184693.
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The Arizona Monsoon Boundary is defined as the boundary separating two distinctly different air masses over Mexico, the southwestern United States, and the adjacent Pacific during the summer. The structure and dynamics of this boundary are examined by cross-sectional analysis using three different data sources: (1) a time-height cross section, constructed using radiosonde observations, at the time the boundary initially passed through Tucson in 1984; (2) a composite cross section through the boundary, constructed from the Fleet Numerical Oceanography Center analysis; and (3) a cross section through the boundary using high-resolution fields of temperature, moisture, and geopotential height obtained from the VISSR Atmospheric Sounder (VAS). All three cross sections showed similar structure. In some respects, the Arizona monsoon boundary resembles a mid-latitude front with a distinct and relatively sharp air mass change across the boundary, forced almost entirely by confluence. A direct ageostrophic circulation is produced by this forcing, giving weak ascent on the warm, moist side of the boundary. The gradients and flow associated with the composite boundary are weaker, by a factor of four, than those associated with strong mid-latitude fronts. However, the VAS cross section suggests that, at times, the strength of the boundary approaches that of middle-latitude fronts. The wind shear suggested by the composite boundary ought to be unstable to baroclinic or barotropic processes. Disturbances developing along the boundary have been observed. One example of such a disturbance is examined using GOES imagery, lightning strike data, cloud track winds, and VAS data. Satellite images show the disturbance resembling a mid-latitude occluded cyclone, with an apparent low pressure center over northern Baja California and front-like cloud features extending eastward and southward from the low. Lightning strike data show convective activity occurring along the front-like features. Wind data indicate the presence of a cyclonic circulation south of San Diego along the Baja California coast. Cross sections using VAS data suggest that barotropic and baroclinic energy sources are present and suggest the front-like nature of the cloud feature extending southward from the low pressure center. Additionally, a second disturbance that eventually interacted with the monsoon boundary is briefly examined using satellite imagery.
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Smith, Walter Prestont. "Tropical squall lines of the Arizona monsoon." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184868.
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Squall lines possessing nearly all the characteristics of tropical squall lines occasionally develop during the summer monsoon over southern Arizona and northwestern Mexico. Initial thunderstorm formation is over the mountains along the Continental Divide in the late afternoon. Satellite imagery, cloud-to-ground lightning strike data, and surface observations indicate the squall lines move from east to west or northeast to southwest by discrete propagation faster than all the winds below 20 kPa so that most of the anvil clouds lag behind. The synoptic-scale circulation is anomalous with a strong ridge located over the western United States and a deep trough located over the eastern United States. West to northwest winds are found in the boundary layer over southern Arizona and northwest Mexico while a deep layer of east winds are observed above. As a result, most of the environmental wind shear is confined to the lowest 2.5 km above the ground. The low-level wind shear seems to be required for the westward propagation of thunderstorms and the formation of the squall lines. Extremely dry midtropospheric air develops in the easterly flow through some combination of advection and subsidence and also appears to be an important factor in the development of the squall lines. A two-dimensional, nonhydrostatic, numerical model was able to simulate many of the features observed in these squall lines. Solar heating of the elevated terrain in the model caused the initial thunderstorm to develop over the Continental Divide. Continued development of new thunderstorms to the west of the Divide produced a squall line that travelled westward by translation of cells and discrete propagation, wherein new cells would develop 10-25 km ahead of the old ones, at a speed greater than all the winds below 30 kPa. Upward motion produced by westward propagating gravity waves and by the strong low-level convergence found just ahead of the gust front appeared to cause several episodes of discrete propagation. The creation of horizontal potential temperature gradients and the vertical and horizontal advection of preexisting vorticity gradients combined to produce the vorticity field associated with the rear inflow jet that developed beneath the simulated squall line.
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Shareef, Ali. "Numerical Analysis of Convective Storm Development over Maldives." Thesis, University of Canterbury. Geography, 2009. http://hdl.handle.net/10092/3026.
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In the Asian and other monsoon regions of the world most of the severe weather observed is local or mesoscale in nature. Forecasting convective storms or mesoscale systems in the monsoon regions, especially in the tropics, has always been a challenging task to operational meteorologists. Maldives Islands, being situated in the tropical Indian Ocean, are affected by monsoon depressions and tropical cyclones. Thunderstorms and the passage of squall lines are well known sources of heavy rainfall. However, due to the lack of professional people and necessary equipment the weather systems around these islands are seldom studied. Therefore the aim of this thesis is to investigate whether the small islands can create sufficient perturbations in the mesoscale environment to result in the development of convective systems. In this regard, two numerical models, Weather Research and Forecasting model (WRF version 2.2.1) and Regional Atmospheric Modelling System (RAMS version 6.0) were used in this study. Two experiments were performed using the WRF model. In the first experiment, a case study was investigated where the selected day experienced heavy rainfall and thunderstorms. In the second experiment, the same case study was used but with the topographical and surface properties removed in order to investigate the influence of the island in modifying the mesoscale environment. All the experiments were initialized using the re-analysis data from NECP. WRF was able to predict the large scale synoptic features with reasonable accuracy when compared to the observations. Development of the boundary layer and the downstream advection of the temperature anomaly generated by the island were well represented. However, the magnitude of the effects was shown to be weak, probably due to the influence of large scale synoptic features. Even though the model was able to predict the large scale features and some of the mesoscale features, it did not predict any storm development and underestimated the precipitation. Therefore, it was decided to idealize the storm development using the RAMS model. RAMS model was used in a two-dimensional framework. The model was initialized horizontally homogenous using a single sounding and six simulations were performed. The simulation results clearly depicted that the small island can generate its own circulation and influence the mesoscale environment. The daytime heating of the island and the downstream advection of the temperature anomaly in a moist unstable atmosphere could trigger a thunderstorm later in the day. The storm becomes mature approximately 40-80 km offshore. This also suggests that triggering of a storm on one side of an atoll could influence the islands on the downstream side. Sensitivity of storm development to the thermodynamics showed that even with an unstable atmosphere, enough moisture in the lower and mid-troposphere is needed to trigger the storm. Sensitivity to the change of SST showed that convective development was suppressed with a drop of 1 oC. However, this needs further investigation. Assessment of sensitivity to the size of the island showed that the time of triggering of the storm was later and the scale of influence was smaller with a smaller island.
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Diniz, Gabriel Sousa. "High energy emissions from thunderstorms: HEETs, from photons to neutrons toward the ground." Instituto Nacional de Pesquisas Espaciais (INPE), 2016. http://urlib.net/sid.inpe.br/mtc-m21b/2016/02.04.22.21.
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Thunderstorms are the starting point of several intense phenomena such as gamma rays and X rays, neutron, positron and electron emissions. The X rays and gamma rays have energies that may reach 100 MeV. The neutron emissions may be created by energetic gamma ray photons interacting with the air via Giant Dipole Resonance, a photonuclear reaction, related to thunderstorms and lightning in a way that is not completely understood yet. In this work neutrons were assumed to be created by gamma ray photons in the energy range of 10-30 MeV emitted by leader discharges. Their production and propagation toward the ground were investigated using computer simulations. Cross sections data banks were analyzed to provide estimations on the neutrons creation probability. The analysis revealed that the probability per collision of a photonuclear occurs varies between 0 and 3.2\% through the energy range of 10 and 30 MeV. The photons mean free path within this energy range was analyzed together with the atmospheric density profile showing that for photon source altitudes above 1 km, the photons with this energy pass through a sufficiently high number of mean free path to ensure a collision. The free software EGS5 was used to treat the photons and electrons motion through the atmosphere in the intent of analyze the spread of the beams, that were assumed to be monodirectional. The photon beam presented an aperture of 2-6$^{o}$ $\pm$ 2$^{o}$ while the electron beam was broader showing an aperture of 11-13$^{o}$ $\pm$ 3$^{o}$. Since EGS5 does not take into account neutron production and motion, the neutron analysis was done with the FLUKA software simulating a photon beam in different initial heights and estimating the photon and neutron ground detection. FLUKA simulations have shown that neutrons are distributed at the ground within a radius of 2 km away from the source axis. The neutrons reached ground with a rate of 10$^{-4} $-10$^{-2}$ neutrons per gamma, which agrees with the cross section analysis done upon the neutron production. The neutron number decrease was used to estimate an upper limit of 5 km for the altitude of a punctual photon source that is capable of generating ground detectable neutrons.Nuvens de tempestade são o início de vários fenômenos intensos como os raios gama e raios X, bem como de emissões de nêutrons, pósitrons e elétrons. As emissões de raios X e raios gama possuem energias que alcançam 100 MeV. As emissões de nêutrons podem ser criadas por interações entre raios gamma com o ar através da Ressonância Gigante de Dipolo, uma reação foto-nuclear, relacionadas com as nuvens de tempestade e com raios de um modo ainda não totalmente compreendido. Neste trabalho supõe-se que os nêutrons são criados por fótons de raios gamma com energia entre 10-30 MeV emitidos durante a propagação do líder negativo. A produção e a propagação pelo ar destes nêutrons foram investigadas utilizando simulações computacionais. Bancos de dados de seções de choque foram analisados para estimar a probabilidade por colisão de uma reação foto-nuclear acontecer. A análise revelou que essa probabilidade varia entre 0\% e 3.2\% para fótons com energia entre 10 e 30 MeV. O livre caminho médio dos fótons no intervalo de energia de 10-30 MeV foi analisado junto com o perfil de densidade atmosférica. A análise mostrou que para fótons com altitude inicial acima de 1 km, eles passam por livres caminhos médios o suficiente para a probabilidade de ocorrência de ao menos uma colisão ser garantida. O software livre EGS5 baseado no método Monte Carlo foi usado para tratar o movimento dos fótons e elétrons pela atmosfera no intuito de estudar a difusão de feixes monodirecionais dessas partículas. Foi observado que o feixe de fótons possui uma abertura entre 2-6$^{o}$ $\pm$ 2$^{o}$ enquanto o feixe de elétrons possui uma abertura de 11-13$^{o}$ $\pm$ 3$^{o}$ . A análise de nêutrons foi feita com o software FLUKA simulando um feixe de fótons em diferentes altitudes iniciais e estimando a detecção de fótons e nêutrons no solo. As simulações do FLUKA mostraram que os nêutrons se distribuem no solo em uma distância radial da fonte de 2 km, chegando ao solo numa razão entre 10$^{-4}$ até 10$^{-2}$ nêutrons/fótons, o que concorda com a análise das seções de choque. A diminuição dos nêutrons detectados em solo permitiu a estimativa de uma altura limite de 5 km para uma fonte pontual de fótons capaz de produzir nêutrons detectáveis em solo.
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White, Trevor Stewart. "Dual-Doppler Derived Vorticity as a Predictor of Hail Size in Severe Thunderstorms." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74927.
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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
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Smith, Bryan T. "Climatology of cool season severe thunderstorms in the east-central United States, 1995-2002." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1380107.
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While the spring and summer months are typically the severe weather climatological peak for the East-Central United States, severe thunderstorms and deadly regional tornado outbreaks can occur during the cool season months (e.g., October-March). In an effort to better document and improve operational forecasting of these events, this study focuses on cool season severe thunderstorms in the Ohio and Tennessee Valleys during the 1995-2002 cool seasons.Most severe thunderstorm and tornado events in the East-Central United States during the cool season are characterized by a high frequency of wind reports compared to hail and tornado reports. All severe report classes (i.e. tornadoes, hail, and wind) displayed a frequency tendency to remain high in the late evening and overnight hours. Additionally, it was found that tornado occurrence typically came in the form of a tornado outbreak. Additionally, when tornadoes did occur, they were found to be statistically more intense than tornadoes outside of the EC region during the same period. It is also concluded tornadoes favor the southern half of the region, whereas hail and wind reports tend to favor the southern two thirds of the region. In examination of cool season supercell characteristics, supercells favors a west-southwest to east-northeast mean motion around 45 mph. The relationship of only 11 percent between the distances of supercell tornado paths to tornadic supercell paths is an operationally important discovery. Knowing on average, how long a cool season supercell tornado is on the ground with respect to the parent supercell can aid operational warning decisions.Department of Geography
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Rae, Kevin Julian. "A modified Supercell Composite Parameter for supercell thunderstorms over the Gauteng Province, South Africa." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/45918.
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South Africa is a country prone to frequent outbreaks of thunderstorms which are often of a severe nature. Supercell thunderstorms are a particular class of thunderstorm which are typically long-lived and are associated with severe thunderstorm phenomena in as many as 9 out of 10 instances. In particular, the southern African moist Highveld climatological region is known to experience one of the highest rates of occurrences of thunderstorms and lightning within southern Africa and indeed the world. The domain for this Highveld-based study chiefly encompassed the industrialised metropolis of the Gauteng province. The population and infrastructure of this province are vulnerable to a variety of adverse effects relating to severe thunderstorms, comprising one or more of strong damaging winds, large hail, urban flooding or even tornadoes of varying intensity. In this study a sample of 15 supercell (SUP) proximity soundings of upper air data for Irene, Gauteng was compared against a large, independant sample of 510 Irene proximity soundings for austral summers during the period 2007 to 2011, representing non-supercell (NON-SUP) thunderstorm days. Hypothesis testing as well as box and whisker representations of the SUP versus NON-SUP samples were applied to various thunderstorm parameters to determine which SUP parameters exhibit the greatest statistical departure from their NON-SUP counterparts. Selected quartiles of SUP parameters so identified were further utilised to formulate a Modified Supercell Composite Parameter (MSCP) tuned to Gauteng supercells. MSCP as well as formulations of the Supercell Composite Parameter (SCP) were subsequently applied to five case-study events where some of the events were associated with observed supercells and some not.
The results strongly indicated that, in a short-term forecast context, MSCP has useful discriminatory ability to provide quantitative predictive guidance as to the relative likelihood of the development of supercell thunderstorms in the Gauteng area. Prior to this research, neither the SCP nor the MSCP were in operational use in South Africa. To the best of the author’s knowledge this work is the first of its kind in southern Africa, especially with consideration to the unique high-altitude Highveld domain of the Gauteng province. In the light of the research results presented herein, it is proposed that MSCP be jointly implemented on point-based (upper air sounding analysis) platforms as well as that of gridpoint-based (deterministic NWP) platforms for short-term predictions of supercell-type thunderstorm conditions in Gauteng province.Dissertation (MSc)--University of Pretoria, 2014.
tm2015
Geography, Geoinformatics and Meteorology
MSc
Unrestricted
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Nordin, Stensö Isak. "Predicting Tropical Thunderstorm Trajectories Using LSTM." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231613.
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Thunderstorms are both dangerous as well as important rain-bearing structures for large parts of the world. The prediction of thunderstorm trajectories is however difficult, especially in tropical regions. This is largely due to their smaller size and shorter lifespan. To overcome this issue, this thesis investigates how well a neural network composed of long short-term memory (LSTM) units can predict the trajectories of thunderstorms, based on several years of lightning strike data. The data is first clustered, and important features are extracted from it. These are used to predict the mean position of the thunderstorms using an LSTM network. A random search is then carried out to identify optimal parameters for the LSTM model. It is shown that the trajectories predicted by the LSTM are much closer to the true trajectories than what a linear model predicts. This is especially true for predictions of more than 1 hour. Scores commonly used to measure forecast accuracy are applied to compare the LSTM and linear model. It is found that the LSTM significantly improves forecast accuracy compared to the linear model.Åskväder är både farliga och livsviktiga bärare av vatten för stora delar av världen. Det är dock svårt att förutsäga åskcellernas banor, främst i tropiska områden. Detta beror till större delen på deras mindre storlek och kortare livslängd. Detta examensarbete undersöker hur väl ett neuralt nätverk, bestående av long short-term memory-lager (LSTM) kan förutsäga åskväders banor baserat på flera års blixtnedlslagsdata. Först klustras datan, och viktiga karaktärsdrag hämtas ut från den. Dessa används för att förutspå åskvädrens genomsnittliga position med hjälp av ett LSTMnätverk. En slumpmässig sökning genomförs sedan för att identifiera optimala parametrar för LSTM-modellen. Det fastslås att de banor som förutspås av LSTM-modellen är mycket närmare de sanna banorna, än de som förutspås av en linjär modell. Detta gäller i synnerhet för förutsägelser mer än 1 timme framåt. Värden som är vanliga för att bedöma prognosers träffsäkerhet beräknas för att jämföra LSTM-modellen och den linjära. Det visas att LSTM-modellen klart förbättrar förutsägelsernas träffsäkerhet jämfört med den linjära modellen.
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Clements, Nathan Chase. "The warning time for cloud-to-ground lightning in isolated, ordinary thunderstorms over Houston, Texas." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2421.
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Weaver, James C. "The impact of synoptic-scale flow on sea breeze front propagation and intensity at Eglin Air Force Base." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FWeaver.pdf.
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Prociv, Kathryn A. "Terrain and Landcover Effects of the Southern Appalachian Mountains on the Low-Level Rotational Wind Fields of Supercell Thunderstorms." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32463.
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That tornadoes cannot occur in mountains due to disruptive influences of the complex terrain is a common misperception. Multiple tornadoes occur each year in mountainous environments, including the Appalachian Mountains. Copious research examines the influences of complex terrain on large severe weather systems such as multicell convective systems and squall lines, but research is lacking investigating this same relationship for smaller-scale severe weather phenomena like supercells and tornadoes. This study examines how complex terrain may have influenced the rotational low-level wind fields of fourteen supercell thunderstorms in the Appalachians. The terrain variables include elevation, land cover, slope, and aspect. Using GIS mapping techniques, the individual storm tracks were overlaid onto elevation, land cover, slope, and aspect layers; points along the storm tracks were measured to correlate storm intensities with the underlying terrain. Hypotheses predict that lower elevations, areas of shallower slopes, agricultural land covers, and terrain features with a southeasterly orientation represent terrain variables that would enhance low-level rotation in the lower levels. Results indicate that elevation has a significant impact on storm rotational intensity, especially in mountainous regions. Lower and flatter elevations augment storm rotational intensity, and higher elevations decrease storm rotational intensity. Additionally, northern and western facing slopes exhibited a negative relationship to storm intensity. A qualitative examination revealed vorticity stretching to be evident in eight of the fourteen storms; with vorticity stretching evident on both southeasterly and northwesterly slopes. Future research on appropriate scale for storm-terrain interactions could reveal even stronger relationships between topography and supercell thunderstorms.Master of Science
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Henderson, Jeffrey Michael. "Collaborative En Route Airspace Management Considering Stochastic Demand, Capacity, and Weather Conditions." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26536.
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The busiest regions of airspace in the U.S. are congested during much of the day from traffic volume, weather, and other airspace restrictions. The projected growth in demand for airspace is expected to worsen this congestion while reducing system efficiency and safety. This dissertation focuses on providing methods to analyze en route airspace congestion during severe convective weather (i.e. thunderstorms) in an effort to provide more efficient aircraft routes in terms of: en route travel time, air traffic controller workload, aircraft collision potential, and equity between airlines and other airspace users. The en route airspace is generally that airspace that aircraft use between the top of climb and top of descent.
Existing en route airspace flight planning models have several important limitations. These models do not appropriately consider the uncertainty in airspace demand associated with departure time prediction and en route travel time. Also, airspace capacity is typically assumed to be a static value with no adjustments for weather or other dynamic conditions that impact the air traffic controller. To overcome these limitations a stochastic demand, stochastic capacity, and an incremental assignment method are developed. The stochastic demand model combines the flight departure uncertainty and the en route travel time uncertainty to achieve better estimates for sector demand. This model is shown to reduce the predictive error for en route sector demand by 20\% at a 30 minute look-ahead time period.
The stochastic capacity model analyzes airspace congestion at a more macroscopic level than available in existing models. This higher level of analysis has the potential to reduce computational time and increase the number of alternative routing schemes considered. The capacity model uses stochastic geometry techniques to develop predictions of the distribution of flight separation and conflict potential. A prediction of dynamic airspace capacity is calculated based on separation and conflict potential.
The stochastic demand and capacity models are integrated into a graph theoretic framework to generate alternative routing schemes. Validation of the overall integrated model is performed using the fast time airspace simulator RAMS. The original flight plans, the routing obtained from an integer programming method, and the routing obtained from the incremental method developed in this dissertation are compared. Results of this validation simulation indicate that integer programming and incremental routing methods are both able to reduce the average en route travel time per flight by 6 minutes. Other benefits include a reduction in the number of conflict resolutions and weather avoidance maneuvers issued by en route air traffic controllers. The simulation results do not indicate a significant difference in quality between the incremental and integer programming methods of routing flights around severe weather.Ph. D.
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Crimmins, Michael. "Arizona and the North American Monsoon System." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/146919.
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Ott, Lesley Elaine. "An analysis of convective transport, lightning NOx̲ production, and chemistry in midlatitude and subtropical thunderstorms." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4085.
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Thesis (Ph. D.)--University of Maryland, College Park, 2006.Thesis research directed by: Atmospheric and Oceanic Sciences. Title from t.p. of PDF. On t.p. "x̲" is subscript. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Buffalo, Kurt Matthew. "Environmental control of cloud-to-ground lightning polarity in severe storms." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2016.
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Jurecka, Joseph William. "An evaluation of lightning flash characteristics using LDAR and NLDN networks with warm season southeast Texas thunderstorms." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85994.
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A comparison of flash parameters from the National Lightning Detection
Network (NLDN) is made with data obtained from the Houston Lightning Detection and
Ranging II (LDAR) network. This research focuses on relating the peak current and
number of strokes in a negative flash (multiplicity) of lightning with the spatial extent
and mean altitude of three-dimensional lightning in 1407 flashes as mapped by the
LDAR network. It is shown that increasing negative multiplicities over the range two
through ten exhibit, on average, a higher flash extent with higher multiplicities. Singlestroke
flashes have mean heights of nearly 2 km greater. Higher order multiplicities (2
to 10+) were correlated with mean source heights near 8 km. Increasing multiplicity
tends to be associated with greater flash extents increasing more horizontally than
vertically with a 50% to 70% increase in flash extent. No obvious relationship between
peak current and flash extent was observed. Examining peak current and mean height
shows that low current flashes (<10kA) exhibit higher mean heights. However, this may
be due to intra-cloud only flashes being reported as cloud to ground events by the
NLDN. Bipolar flashes do not show much variation with height and flash extent with the exception of negative-first bipolar flashes, which exhibited mean flash extents twice
that of other types. Finally, the flash detection efficiency is 99.7% within 60 km of the
network center.
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Hitchens, Nathan M. "The possible relationships between atmospheric teleconnections and severe thunderstorm outbreaks in the continental United States." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1339150.
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The purpose of this study is to examine possible relationships between changes in values of teleconnection indices related to the Southern Oscillation Index (SOI), North Atlantic Oscillation (NAO), Pacific-North American (PNA) pattern, and Arctic Oscillation (AO), and outbreaks of severe thunderstorms for specific time periods following such changes. A series of chi-squared tests are performed to determine if statistically significant relationships exist between changes in teleconnection index values and the occurrence of severe thunderstorm outbreaks. Results indicate that changes in the SOI seem to be related to an increase in the frequency of outbreaks that follow in the short-term.Department of Geography
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Zöbisch, Isabella [Verfasser], and George C. [Akademischer Betreuer] Craig. "Thunderstorms: Life cycle analyses and nowcasting based on multi-source data / Isabella Zöbisch ; Betreuer: George C. Craig." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1206096489/34.
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Lad, Manish. "Characterization of Atmospheric Noise and Precipitation Static in the Long Range Navigation (Loran-C) Band for Aircraft." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1102702655.
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Pilewskie, Peter Andrew. "Cloud phase discrimination by near-infrared remote sensing." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184674.
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A ground-based near-infrared spectroradiometer was built and used to measure relative spectral reflectance from cumulus congestus and cumulonimbus clouds during the 1985 and 1986 Arizona summer monsoon seasons. Thermodynamic phase was inferred from spectral features in the regions between 1.55-1.75μm and 2.1-2.3μm where there are distinct differences between absorption in liquid water and ice and absorption by water vapor is very weak. Although liquid water and ice are nearly transparent in the visible, they absorb weakly in the near-infrared and that absorption is amplified by multiple scattering in clouds. Reflectance measurements are simple to make, requiring neither high spectral resolution nor absolute detector response. Three distinct aspects of differences between absorption in liquid water and ice were used to infer phase: (a) Ratio of the signal at 1.65 μm to that at 2.2 μm; (b) Wavelength of peak signal in the 1.65 μm water vapor transmission window; (c) Half-bandwidth of the 2.1-2.3 μm feature. Representative spectra are presented and analyzed on the basis of the predicted behavior of liquid water and ice cloud absorption. The results are consistent with young cumuli rapidly glaciating as they reach cooler levels, well before evidence of anvil formation or fibrous structure, contrary to the notion that phase can be inferred from visible cloud features.
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del, Moral Méndez Anna. "Radar-based nowcasting of severe thunderstorms: A better understanding of the dynamical influence of complex topography and the sea." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670869.
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Natural disasters of hydro-meteorological origin are the biggest risk worldwide. In Catalonia (NE of the Iberian Peninsula), severe weather and flash floods occur each year, resulting in major damage to property, losses in agriculture, and also of human lives. To reduce its impact, we need to improve the early warning systems and storm short-term forecasting. There’s a need to gain in-depth knowledge of severe thunderstorm dynamics, since the current accused conditions of global warming can impact in factors triggering these storms. The main objective of the present thesis is to enhance the knowledge of severe storms dynamics and to improve their identification and monitoring in real time, in order to help prevent their surface effects on the citizens. The project addresses the unresolved problem of storm anomalous motion, as it becomes a great challenge to predict their evolution and impact in the next few hours.
For this purpose, the area of Catalonia has been chosen as the study region of this project, due to the proximity to the sea and complex topography, which are often key factors in varying the weather at a local scale. There is also the advantage of having good radar coverage, which will be the essential tool for characterizing storms.
We first propose a methodology that identifies potentially convective days from daily cumulative rainfall fields, selects them to search for storms, and determines if their motion is anomalous. We have found that the area with the highest convective activity between 2008-2015 in Catalonia was located in the eastern Pre-Pyrenees, due to the possible creation of a convergence line. It has also been identified that there are more convective structures with possible anomalous propagation in summer and spring, with the main patterns being related to splitting, merging, stationarity and elongated storms.
Once the study sample is defined, we have developed an algorithm to improve the identification and tracking of these thunderstorms, especially those with anomalous propagations. The keys of improvement have been based on proposing new techniques in the three main modules; 2D, 3D identification and tracking. In addition, it incorporates alerts before possible cell splitting or merging. These changes have shown that the algorithm is able to faithfully reproduce storm life cycle, correctly identify in advanced anomalous motion, and correctly distinguish storms in highly dense convective situations.
The algorithm has been verified first over 30 severe cases, proving that it can identify anomalous movements with a mean 30-min lead-time, being the splitting, the easiest one to do. It has also been demonstrated a good ability at not only identifying these movements but also separating cases with and without anomalous motion. On the other hand, the algorithm has demonstrated a good performance in cases of heavy rainfall on a Catalan flood-prone coastal area of touristic interest. It is identified that storms are usually organized in convergence lines, and that topography and the sea play a very important role, whether affecting the movement, the time of exposure, or the amount of precipitable water causing flash floods.
Finally, the dual-Doppler technique is applied in Catalonia for the first time. This allows getting complete information of the internal dynamics of a thunderstorm, without the need of running idealized models, and then, getting to know the local topographic influence on the evolution and organization. It is demonstrated that the complex local topography changes and/or amplifies the wind flow inside and near thunderstorms, modifying completely their life cycle and their possible interactions with their neighbor cells. It is also shown that this qualitative improvement into storm-scale dynamic knowledge can improve the nowcasting techniques and the early warning systems in the future.Els desastres naturals d’origen hidro-meteorològic constitueixen el major risc a nivell mundial. A Catalunya, cada any es succeeixen diferents episodis de temps advers i inundacions, provocant també danys importants en béns materials, pèrdues en l’agricultura, o pèrdua de vides humanes. Aquestes dades poden augmentar en les condicions cada cop més acusades d’escalfament global. Per reduir l’impacte d’aquest fenòmens és necessari millorar els sistemes d’alerta primerenca a molt curt termini, així com la monitorització dels sistemes meteorològics causants d’aquests fenòmens. En aquest context l’objectiu principal d’aquesta tesi doctoral es millorar el coneixement profund de la dinàmica de les tempestes severes, la seva identificació, predicció a molt curt termini, i monitoratge a temps real. Assolir aquest objectiu implica millorar la prevenció dels seus efectes en superfície. La tesis aborda una problemàtica encara no resolta sobre el moviment anòmal d’aquestes tempestes, que esdevé un gran repte a l’hora de pronosticar-ne la seva evolució en les properes hores, i per tant, el seu impacte. A més, es centra a Catalunya, degut a la seva proximitat al Mar Mediterrani i la complexa topografia, factors claus resultants en una meteorologia variada quasi a nivell de municipi, on hi ha l’avantatge de disposar d’una bona cobertura radar, eina essencial per la caracterització de les tempestes. Primer, es proposa una metodologia que permet identificar les situacions potencialment convectives a partir de camps de precipitació acumulada diària, seleccionant aquestes per cercar les tempestes i determinar si el seu moviment és anòmal (del Moral et al., 2017). Definida la mostra d’estudi, es desenvolupa un algoritme que permet millorar la identificació i seguiment d’aquestes tempestes, sobretot quan es tracta d’aquelles amb moviment anòmal (del Moral et al., 2018a). El funcionament de l’algorisme es verifica en dos règims de convecció diferent: casos severs d’interior (del Moral et al., 2018b), i pluges intenses a la costa (del Moral et al., 2020a). Finalment, s’introdueix per primer cop en un país sud-Europeu la tècnica dual-Doppler: obtenció de variables dinàmiques dins de les pròpies tempestes a partir d’observacions radar, per a l’estudi de les interaccions de més petita escala (del Moral et al., 2020b).
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Bender, Andréia. "Eventos de tempo severo associados às linhas de instabiliade sobre o estado de São Paulo." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/14/14133/tde-24062013-113838/.
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Neste trabalho foram estudadas as linhas de instabilidade (LI) que atingiram a RMSP, o desenvolvimento de tempo severo associados a estas e a possibilidade de utilizar alguns parâmetros de tempo severo na identificação destes eventos. Foram identificadas 185 linhas no período de 2002 a 2009 através da observação de imagens de satélite. Estas ocorrem durante todos os períodos do ano, embora a frequência seja maior nos meses de verão, em função da maior atividade convectiva nessa estação do ano. Foi identificado que 94 % das LI se deslocaram para leste enquanto apenas 6 % tiveram seu deslocamento para oeste. Testes sobre configurações mais adequadas para a simulação de LI com o modelo BRAMS indicaram que as parametrizações de convecção disponíveis no modelo não são capazes de representar os eventos de forma adequada, havendo a necessidade de aumento na resolução das simulações e forte dependência da parametrização de microfísica. Foi constatado que espaçamentos de grade de oito quilômetros são suficientes para uma boa representação dos eventos. Os testes também indicaram que, dentre as opções disponíveis no modelo, o uso da deformação Anisotrópica para o tratamento dos processos turbulentos é o mais indicado para a simulação de casos de LI. Os parâmetros convectivos mostraram-se bons indicadores de tempo severo na presença de sistemas de origem baroclínica, apresentando valores similares aos encontrados para o HN. Porém, em tempestades onde o efeito termodinâmico é o fator mais importante, como nas tempestades isoladas ou na presença de ZCAS os índices cinemáticos nem sempre são bons preditores de tempo severo. A análise dos parâmetros convectivos obtidos das radiosondagens lançadas na RMSP mostra que, em muitos casos observados de LI, não há valores indicativos de ocorrência de tempo severo, ressaltando a importância do uso de perfis obtidos da modelagem numérica, numa região de abrangência maior, para a obtenção desses índices.A study about the squall lines that reached Metropolitan Area of São Paulo (MASP), the development of severe weather associated with these and the possibility of using some parameters in the identification of severe weather are presented. It was identified a total of 185 squall lines between 2002 and 2009 through the analysis of satellite images. These lines occur during all periods of the year, although the frequency of squall lines is higher in summer months, due to increased convective activity in this season. Also, it was identified that 94 % of the squall lines moved eastward while only 6% of then moved westward. Tests about the most appropriate configuration to the squall lines simulation with BRAMS model indicated that the convective parameterizations available in the model are not able to represent the events in an adequate manner, being necessary to use higher resolutions in the simulations, which creates a stronger dependence on microphysics parameterization. We note that grid spacing as low as eight kilometers are enough for a fair representation of the events. The tests also indicated that, among all the options available in the model for turbulent process the anisotropic deformation is the one that works better in simulating squall lines. The convective parameters proved to be good indicators of severe weather in the presence of baroclinic systems, with similar values to those found for the Northern Hemisphere. However in storms where the thermodynamic effect is the most important factor, as in isolated storms and in the presence of the Southern Atlantic Convergence Zone (SACZ), kinematics indices are not always good predictors of severe weather. The analysis of convective indices, obtained through radiosondes variables launched in the MASP, shows that in many squall line observed cases there is no indication of severe weather occurrence. This fact increases the importance of using the profiles provided by numerical modeling over a larger region to obtain such indices.
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Becerra, Marley. "On the Attachment of Lightning Flashes to Grounded Structures." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8871.
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Ribaud, Jean-François. "Etude tridimensionnelle de l'activité électrique, microphysique et dynamique d'une ligne de grain observée pendant la campagne HyMeX." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30353/document.
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La question de la prévision des évènements fortement précipitants se produisant sur le bassin Méditerranéen est au coeur du programme international HyMeX (Hydrological cycle in Mediterranean EXperiment, http://www.hymex.org/) dont l'un des objectifs est d'améliorer la prévision et la prévention des risques hydrométéorologiques du bassin méditerranéen dans le contexte du changement climatique. Durant l'automne 2012, une campagne de mesures de deux mois dite "Période d'Observation Spéciale" (SOP1) a été menée afin de documenter les conditions propices à la formation et au développement des évènements convectifs de type cévenol souvent responsables de crues dévastatrices. Pendant cette SOP1 un dispositif instrumental sans précédent a été déployé avec notamment pour la première fois sur le sol français un imageur à haute résolution spatio-temporelle permettant d'observer les décharges électriques en trois dimensions : le Lightning Mapping Array (LMA). Cet instrument a été combiné aux radars du réseau ARAMIS de Météo-France, et plus précisément aux radars Doppler à diversité de polarisation dans le Sud-Est de la France qui offrent la possibilité d'obtenir des informations sur le type et la distribution des hydrométéores au sein des systèmes précipitants. La production d'éclairs étant le résultat d'une électrisation issue des interactions microphysiques (collisions entre graupels et cristaux de glace en suspension), une description détaillée des différents types d'hydrométéores présents dans les nuages convectifs est essentielle. Dans cette optique, les algorithmes d'identification des hydrométéores développés par Météo-France ont été évalués puis améliorés. Les résultats de cette étude ont montré que les restitutions entre les différents radars étaient plutôt cohérentes, à condition que l'information sur l'altitude de l'isotherme 0°C soit correcte. Ce travail a ensuite été complété par la création, via une méthode originale, de composites 3D d'hydrométéores permettant de décrire la microphysique majoritairement présente dans les systèmes convectifs observés pendant la campagne HyMeX. La deuxième partie de ce travail s'est basée sur l'exploitation de la synergie radar-LMA sur une ligne de grain observée durant la SOP1 de HyMeX. Les principales informations déduites de ce couplage ont mis en exergue l'importance des processus microphysiques intervenant dans l'électrisation du nuage d'orage, ainsi que l'impact du relief sur l'activité électrique globale du système convectif. Sur les quatre heures de données analysées du 24 Septembre 2012, le déclenchement et la propagation des éclairs ont majoritairement été observés dans les espèces microphysiques que sont le graupel, les cristaux de glace et dans une moindre mesure la grêle. Cette étude souligne également le rôle important de la topographie sur l'activité électrique et montre que le passage d'un faible relief peut dramatiquement influencer la distribution et l'intensité des éclairs dans les régions convectivesThe Hydrological cycle in Mediterranean Experiment (HyMeX, http://www.hymex.org/) is a 10-year research program focusing on the quantification and understanding of the water cycle in the Mediterranean at various time and spatial scales with particular emphasis on high-impact weather events. This study takes place within the framework of the first HyMeX field phase (HyMeX-SOP1), which was conducted in the autumn 2012. The unique and extensive dataset collected during this field campaign offers the possibility to further investigate the complex relationships between cloud microphysics and lightning at play within mesoscale convective systems observed in southern France. With this regard, the present study make the use of a Lightning Mapping Array (LMA) along with operational dual-polarization weather radar. The first instrument allows documenting the three-dimensional lightning activity, whereas the second has the ability to determine the type of hydrometeors within cloud systems. Since the production of lightning is the result of an electrification created by microphysical collisions between graupels and ice crystals in suspension, a highly detailed description of hydrometeor types within convective clouds is needed. With this respect, an improved version of Météo-France hydrometeor classification algorithm was developed and evaluated so as to be able to discriminate between a large number of microphysics species. Overall hydrometeor species retrieved from a pair of neighbouring radars within a common sampling area are consistent from one to another. This study has however pointed out the need to check the consistency related to the identification of 0°C isotherm derived from numerical weather prediction model outputs before to perform hydrometeor identification. As a follow up to this work, a novel interpolation method allowing the remapping of single-radar hydrometeor fields onto a common Cartesian grid was developed in order to get access the three-dimensional hydrometeor distribution within HyMeX convective systems. Another part of this work aims at combining LMA and polarimetric radar observations to infer relationships between the total lightning activity, microphysics, and kinematics within the intense bow-echo system observed above the complex terrain of southern France during HyMeX. Using the synergy between LMA and polarimetric radar data, it is underlined that microphysical processes involved in cloud electrification, along with the impact of the topography play at part onto the global lightning activity. Based on a 4h analysis on the 24 Setptember 2012, it is found that lighting initiation and propagation take preferentially place within graupel, ice and to a lesser extent hail regions. This study also highlights the important role of topography on lightning activity and shows that even a small hill can dramatically influence the distribution and intensity of lightning within convective areas
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Scheffknecht, Phillip. "Characterization of heavy precipitation on Corsica." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30339/document.
Full textAbstract:
Les fortes précipitations sont parmi les phénomènes météorologiques les plus dangereux pouvant causer des dégâts matériels, des blessés et des morts. Le programme de recherche HyMeX (Hydrological cycle of the Mediterranean eXperiment) s'intéresse à leur étude sur le bassin méditerranéen et plus particulièrement sa partie nord occidentale. Les travaux réalisés dans le cadre de cette thèse ont porté en particulier sur l'étude des mécanismes associés aux événements de fortes précipitations (High Precipitation Events, HPE) se produisant en Corse. Une climatologie des HPE en Corse sur une durée de 31 ans a été réalisée ainsi que l'étude détaillée de trois HPEs de l'automne 2012 pendant la campagne de mesures d'HyMeX. Ces trois cas d'études sont abordés par le biais de l'analyse des données et par celui de la modélisation. L'étude climatologique a montré que 173 HPEs (caractérisés par plus de 100 mm de précipitations en 24h) se sont produits en Corse sur la période 1985-2015. Ils sont principalement caractérisés par le fait qu'ils affectent plutôt la partie orientale de la Corse, plus particulièrement son orographie. Ces HPEs se produisent surtout de septembre à décembre avec un maximum en octobre. Une analyse en composantes principales a permis de classer ces événements en trois catégories. Les dépressions méditerranéennes chaudes d'automne, celles d'hiver froides, et une catégorie dite mixte associée aux dépressions atlantiques de grande échelle. Les précipitations les plus fortes sont observées quand l'orographie corse fait obstacle à un flux de sud-est chaud et humide. Les cas d'études présentés sont tous les trois différents en terme de mécanismes impliqués. Le cas du 4 septembre 2012 est associé à une dépression stationnaire donnant des précipitations sur toute la Corse avec un maximum sur le littoral et le relief de l'est de l'île. Celui du 31 octobre correspond à une dépression se déplaçant rapidement et induisant une évolution en plusieurs phases associée à un flux de basse couche initialement de sud-est tournant à l'ouest, associé à des précipitations d'abord convectives le long du relief oriental puis évoluant au fur et à mesure en pluies stratiformes sur l'ouest et le sud-est de l'île. Le dernier cas, du 23 octobre, est composé d'une ligne de cellules convectives résultant d'une convergence stationnaire au sud-est, sous le vent de la Corse. Les cellules convectives sont advectées vers l'île par le flux de sud-est de moyenne et haute altitude. Cette configuration permet la stationnarité de la ligne convective, provoquant un épisode de précipitations relativement court et très localisé. Les résultats de ce travail confirment que le modèle numérique Meso-NH permet de bien simuler ce type de phénomène avec une précision satisfaisante à une résolution horizontale de 2,5 km. Cependant, cette étude met également en évidence l'importance de la bonne représentation des conditions initiales. En outre, la distribution spatiale des précipitations dépend fortement de la représentation de l'orographie dans le modèle et de la résolution horizontale. Elle est améliorée quand on utilise une résolution de 500mHeavy precipitation is one of the primal meteorological reasons for property damage, injuries, and deaths. In the framework of the Hydrological Cycle of the Mediterranean (HyMeX) program, heavy precipitation is analyzed throughout the entire Mediterranean basin with a special focus on the northwestern Mediterranean. This work studies in particular the mechanisms of high precipitation events (HPEs) on Corsica. For this purpose, a 31 year (1985 - 2015) climatology of HPEs on Corsica is presented. In addition, three HPEs during autumn 2012 are analyzed in detail using observations and numerical modeling. A climatology of 173 events shows that the eastern half of Corsica, specifically the orography, is most affected by high precipitation events. The months from September to December, most of all October, are identified as most prone to heavy precipitation events over Corsica. A principal component analysis is used to classify the events into three categories, which correspond to warm autumn and cold winter Mediterranean cyclones as well as a mixed category which contains also larger scale Atlantic cyclones. The heaviest precipitation is observed when warm moist southeasterly flow encounters the Corsican orography. In addition, three case studies are presented, each with different mechanisms involved. A stationary cyclone on 4 September 2012 led to widespread precipitation over Corsica with the most intense rain observed over the east of the island, along the coast and the orography. On 31 October, a fast moving cyclone caused a multi-phase event, which was characterized by low level wind turning from southeast to west while precipitation gradually changed from convective along the orography in the east of the island to stratiform mainly over the west and southwest. The last event, 23 October 2012, was comprised of a line convective cells which formed over stationary lee side convergence southeast of Corsica. The convective cells were advected toward the island by the mid- and upper level southeasterly wind. These conditions allowed the convective line to remain stationary, resulting in a highly localized and relatively short event. The findings confirm that the numerical model Meso-NH is well capable of simulating such events with satisfactory precision at a grid spacing of 2.5 km. However, the studies also underline the importance of well captured initial conditions. Additionally, the spatial distribution of precipitation is highly dependent on the representation of the orography in the model as well as the horizontal grid spacing and is improved when using a horizontal grid spacing of 500 m instead
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Wallentine, Kari D. "Thunderstorm phobia in dogs." Thesis, Kansas State University, 2008. http://hdl.handle.net/2097/11975.
Full textAbstract:
Master of ScienceDepartment 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.
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Wurman, Joshua Michael Aaron Ryder. "Forcing mechanisms of thunderstorm downdrafts." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/59043.
Full textAbstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Includes bibliographical references (p. 151-156).
by Joshua Michael Aaron Ryder Wurman.
Sc.D.
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McConville, Alastair Charles. "The physical simulation of thunderstorm downbursts." Thesis, University of Birmingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.736955.
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Barrett, Kevin M. Greene Donald Miller. "The county bias of severe thunderstorm warnings and severe thunderstorm weather reports for the Central Texas region." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5161.
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Hsieh, Huey-Hong. "Stochastic daily thunderstorm generation in southeast Arizona." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280114.
Full textAbstract:
Thunderstorm rainfall in semi-arid areas has very high spatial and temporal variability. Knowledge of the spatial characteristics of thunderstorm rainfall is important for the increasing demands of distributed hydrological modeling. Rainfall data from the semiarid USDA-ARS Walnut Gulch Experimental Watershed (WGEW) were used to investigate the spatial characteristics of thunderstorm rainfall in southeast Arizona and to develop a daily thunderstorm rainfall generator. WGEW has a very dense rain-gage network (1 gage per 2 km²) and very comprehensive historical records (over 40 years). These data were used to identify the following physical characteristics of thunderstorm rainfall: the transition probabilities, thunderstorm cell size, orientation, maximum rainfall depth within a storm cell and storm center location. The following statistical characteristics were identified through an analysis of the WGEW data: the storm center locations on WGEW have a Poisson distribution, the maximum depth within a storm cell has a lognormal distribution, the shape of a storm cell is elliptical with an average major axis length to the minor axis length ratio of 1.55 and the orientation of a storm cell is primarily NW or NE. The storm coverage and the maximum rainfall depth within a storm cell have a linear relationship after a logarithmic transformation. Storm occurrences have higher frequencies during the last two weeks of July and the first two weeks of August than other wet periods (July ∼ September). The stochastic daily summer rainfall generator being developed based on the statistical characteristics above was tested by comparing the simulation results with long-term historical records of representative gages on WGEW.
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ZUZUL, JOSIP. "Characterization of thunderstorm downburst winds through CFD techniques." Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1081542.
Full textAbstract:
The characteristic wind field of a certain region is mostly governed by the climatology of its larger scale area. In the case of mid-latitude regions (e.g. Europe), their climatology is determined by the extra-tropical cyclones at the larger synoptic scale. Atmospheric boundary layer (ABL) winds based on synoptic-scale structures are hence considered as the foundation for codes and standards used to assess the wind loading of structures and to design structures to prevent wind-related damage accordingly. In addition to the ABL winds, the mid-latitude regions are also prone to winds of a non-synoptic origin at the mesoscale level, with thunderstorm outflows or downbursts being the representative of such non-synoptic wind action. Since they are determined by a set of features that makes them fundamentally different from the ABL winds, downbursts can produce the corresponding wind action that is often fatal to low-rise and mid-rise structures. On these grounds, a comprehensive initiative to enable a better understanding of fundamental downburst flow features relevant for the structural loading was framed under the umbrella of the ERC THUNDERR Project. The present thesis, as the numerical modeling part of the THUNDERR Project framework, aims to address the physical characteristics of thunderstorm downbursts through the application of Computational Fluid Dynamics (CFD) technique. The focus of this work is placed on the CFD reconstruction of experimental tests of the reduced-scale thunderstorm downbursts carried out in the WindEEE Dome Research Institute (University of Western Ontario, Canada). Although they recreate the downburst flow field, the experimental analysis is restricted to the limited number of probe points. In that perspective, CFD allows expanding the analysis of experimental tests to the entire flow field, which can reveal phenomenological aspects that are either challenging or impossible to retrieve from experimental tests only. Two fundamental downburst scenarios were analyzed: (i) an isolated vertical downburst, and (ii) a downburst embedded inside the approaching ABL flow. For that purpose, three CFD approaches of a ranging complexity level were adopted. The unsteady Reynolds-Averaged Navier-Stokes (URANS), hybrid Scale-Adaptive Simulations (SAS), and Large-Eddy Simulations were used, and their overall reliability was examined. Theimplications of the WindEEE Dome specific geometrical features (i.e. bell-mouth inflow nozzle) on the downburst flow reconstruction by the facility were further discussed. The bulk of the thesis discusses the dominant flow features of the downburst with the particular emphasis on the dynamics of dominant vortex structures (i.e. primary vortex, secondary vortex, trailing ring vortices) and their spatio-temporal influence on the vertical profiles of radial velocity component. The non-dimensional flow characteristics of interest were evaluated such as the trajectory of the primary vortex and the spatial dependence of the velocity of primary vortex propagation. Analyses were further extended for the case of a joint downburst and ABL wind interaction to address the dynamics between two different wind fields, and the genesis of the worst condition in terms of the maximum radial velocity due to the ABL wind entrainment was discussed. The flow field was analyzed across various azimuth angles with respect to the ABL flow to report on the flow asymmetry, and general implications of such downburst configuration on spatio-temporal evolution of wind velocity profiles which can produce severe conditions for low-rise and mid-rise structures.