94 research outputs found

    Relationship between hailfall intensity and hail damage on ground, determined by radar and lightning observations

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    WetterradargerĂ€te werden mittlerweile in vielen LĂ€ndern zur Beobachtung und Messung von HagelstĂŒrmen verwendet und liefern einen detaillierten Überblick ĂŒber die Entwicklung und die Struktur von starken Gewittern. Viel Aufwand wurde in die quantitative Messung von HagelschlĂ€gen und Kurzfristprognosen (Nowcasting) von hageltrĂ€chtigen Gewittern investiert, was fĂŒr nationale Wetterdienste und FlughĂ€fen (Warnungen), die Landwirtschaft (Hagelschutz) und Versicherungen (SchadenabschĂ€tzung und PrĂ€vention) von grossem Interesse ist. Obwohl Dual-Polarisation Techniken in letzter Zeit entscheidend verbessert wurden, basieren Methoden zur Hagelerkennung und –messung immer noch auf Single-Polarisations RadargerĂ€ten. Eine der besten Methoden zur Bestimmung der HagelintensitĂ€t mit Single-Polarisation RadargerĂ€ten ist die kinetische Hagelenergie, die aus der RadarreflektivitĂ€t berechnet wird und das gesamte Hagelvolumen pro FlĂ€che reprĂ€sentiert. Es hat sich gezeigt, dass die radarvermessene kinetische Hagelenergie (EKINPIX) gut mit Bodenmessungen von Hagel (Hailpads) und HagelschĂ€den an landwirtschaftlichen Kulturen korreliert. Aufgrund der guten Beziehung zwischen radar- und bodenvermessener HagelintensitĂ€t, wird EKINPIX in dieser Dissertation in Beziehung zu HagelschĂ€den an Autos, an GebĂ€uden und zur HĂ€ufigkeit von Wolken-Boden Blitzen (WB) gesetzt und anhand einer grossen Anzahl Hagelzellen analysiert. Die Dissertation besteht aus den folgenden drei Teilen: einer EinfĂŒhrung, drei wissenschaftlichen Publikationen (eingereicht oder publiziert in (Athmospheric Research) die in einzelnen Kapiteln wiedergegeben sind, und einem abschliessenden Kapitel, in dem zwei methodische AnsĂ€tze wie aus rĂ€umlichen Verteilungen von WB Blitzen gesamte HagelflĂ€chen abgeleitet werden könnten. Artikel 1 zeigt die Beziehung zwischen HagelintensitĂ€ten und HagelschĂ€den an Autos, wĂ€hrend in Artikel 2 der Zusammenhang mit SchĂ€den an Wohn- und LandwirtschaftsgebĂ€uden untersucht wird. Die Radardaten stammen vom C-Band Doppler-Radar, der von der Eidgenössischen Technischen Hochschule (ETH) in der NĂ€he von ZĂŒrich (Schweiz) betrieben wird. HagelschĂ€den an Autos waren durch die Winterthur Versicherungen (1992-1998) und HagelschĂ€den an GebĂ€uden durch verschiedene Kantonale GebĂ€udeversicherungen (1992-1999) erhĂ€ltlich. Die Beziehung zwischen HagelintensitĂ€ten (EKINPIX) und SchĂ€den an Autos (GebĂ€uden) wurden fĂŒr 12 (neun) Hagelzellen analysiert, mit den folgenden Resultaten: Da das Ausmass eines Hagelschadens sehr stark vom Exposure und den physikalischen Eigenschaften der versicherten Objekte abhĂ€ngt, wurden verschiedene Annahmen getroffen und Vereinfachungen eingefĂŒhrt. Die Beziehung zwischen den mittleren SchĂ€den und EKINPIX hĂ€ngt von der Hagelsaison ab: Hagelzellen der Hauptsaison (15. Juni-15. August) produzierten generell höhere SchĂ€den als Gewitter der Nebensaison (vorher und nachher). Ein saisonaler Unterschied in der HagelintensitĂ€t zeigt sich auch aus der Anzahl und der maximalen Hagelkorngrösse von Hailpad Daten, die aus dem Grossversuch IV stammen, welcher in der Zentralschweiz durchgefĂŒhrt wurde (1976-1983). Die nicht-linearen Beziehungen zwischen EKINPIX und den Schadenvariablen lassen sich am besten mit logistischen Funktionen beschreiben, wobei Korrelationskoeffizienten von 0.80 resultieren. Nach entsprechender Verifikation und Kalibrierung generierten die logistischen Funktionen fĂŒr die Schadenrate (VerhĂ€ltnis zwischen SchĂ€den und Gesamtversicherungssumme) SchĂ€den an Wohn- und LandwirtschaftsgebĂ€uden, die in der Grössenordnung der tatsĂ€chlich vorgekommenen SchĂ€den liegen. Der relative Fehler zwischen realen und mit den Schadenfunktionen geschĂ€tzten SchĂ€den liegt fĂŒr die stĂ€rksten StĂŒrme unter 30%. Die erarbeiteten logistischen Schadenfunktionen zwischen radarvermessener kinetischen Hagelenergie und HagelschĂ€den könnten von Versicherungen zur Bestimmung von maximal möglichen SchĂ€den (PMLs) gebraucht werden, indem eine radarvermessene Hagelzelle ĂŒber ein Auto- und/oder GebĂ€udeportefeuille eines bestimmten Gebietes (z.B. einer grösseren Stadt) verschoben werden kann. In Artikel 3 werden WB Blitze, die von den Blitzmessnetzen der Schweiz und SĂŒddeutschland geortet wurden, miteinander verglichen, um eine Angabe ĂŒber die relative Erfassungseffizienz zu erhalten. WB Blitzmessungen des Schweizer Ortungssystems werden einzelnen Hagelzellen (5 min. Auflösung) zugeordnet, so dass der gesamte Lebenszyklus einer Zelle erfasst und in Beziehung zur radarvermessenen kinetischen Hagelenergie (ETH C-Band Doppler-Radar) gesetzt werden kann. Die Auswertung von 41 Hagelzellen die ĂŒber das Schweizer Mittelland gezogen sind (1992-1995), zeigt die folgenden Resultate: Die totale kinetische Hagelenergie steht in einer linearen Beziehung (Korrelationskoeffizient von 0.95) mit der totalen Anzahl negativer WB Blitzen (–WB). Kein direkter Zusammenhang wurde dagegen mit der Anzahl positive geladener WB Blitzen (+WB) gefunden, obwohl zwischen verschiedenen Gewittertypen unterschieden wurde. Positionen von maximaler HagelintensitĂ€t korrelieren mit zeitlichen (0.88) und rĂ€umlichen (0.84) Höchstwerten in der HĂ€ufigkeit von –WB Blitzen. Die meisten Hagelzellen (66%) zeigen, dass –WB Blitze im Mittel 22 min. (0-65 min.) und 19 km (3-58 km) vor der höchsten HagelintensitĂ€t vorkommen. Im Bezug zur maximalen Hagelenergie zeigt sich eine grosse Varianz in Positionen von Höchstwerten in der Anzahl von +WB Blitzen. In schwachen Hagelzellen befindet sich der Höchstwert von +WB Blitzen im Mittel 10 min. vor und 3.5 km nach der höchsten HagelintensitĂ€t. In grossen isolierten Zellen liegt hingegen die Position der meisten +WB Blitze 30 min. und 45 km nach der höchsten HagelintensitĂ€t. Die Resultate der relativ grossen Anzahl untersuchter Gewitter bestĂ€tigen den Einfluss des nicht-induktiven Graupel-Eis Ladungsmechanismus. Dieser erklĂ€rt die Tatsache, dass die Mehrheit der –WB Blitze zu Beginn der Gewitterentwicklung vorkommen, wĂ€hrend die meisten +WB Blitze eher am Ende der GewittertĂ€tigkeit, wĂ€hrend einer Umkehrung der Ladungsteilung beim Ausfall des Niederschlags, auftreten. Die zeitliche und rĂ€umliche Beziehung zwischen Höchstwerten von WB Blitzen und maximaler HagelintensitĂ€t könnte in der Zukunft fĂŒr die Verbesserung der Kurzvorhersagen (Nowcasting) von starken Gewittern verwendet werden, speziell durch eine frĂŒhere Erkennung eines Hagelschlags anhand von WB-Blitz Informationen. Im letzten Kapitel wird die rĂ€umliche Beziehung zwischen Mustern von –WB Blitzen und radarvermessener kinetischer Hagelenergie fĂŒr 18 ausgewĂ€hlte Hagelzellen untersucht. Kreuzkorrelationen zwischen den Blitz- und Energiemuster ergeben Koeffizienten zwischen 0.33 und 0.66, was ein vielversprechender Ansatz fĂŒr eine direkte Bestimmung von HagelflĂ€chen mittels Blitzdaten ist. Zwei methodische AnsĂ€tze zur rĂ€umlichen Verteilung der Hagelenergie werden in diesem Kapitel diskutiert, wobei die vollstĂ€ndige Ausarbeitung der Methoden nicht mehr im Rahmen dieser Arbeit liegt. Falls dies jedoch gelingt, können HagelflĂ€chen fĂŒr grosse Gebiete bestimmt werden, ohne direkt auf Radardaten angewiesen zu sein.Weather radars are now available in many countries for operational observations and measurements of hailstorms and provide detailed information on the formation and structure of severe thunderstorms. Much research has been devoted to the quantitative measurement of hailfalls and the nowcasting of hail-bearing thunderstorms which is of interest for national weather services and airports (warning), the agricultural community (protection) and the insurance industry (damage estimation and mitigation). Although dual-polarization techniques have been improving in recent years, hail detection and measuring methods still have to rely on single-polarization radars. One of the most successful methods to derive hailfall intensities from single-polarization radars is hail kinetic energy that is calculated from radar reflectivity measurements and represents the total volume of hailfall per surface unit. Radar-derived hail kinetic energy (EKINPIX) showed valuable results in relation to ground-based measurements of hailfalls (hailpads) and amounts of hail damage to various crops. Based on the good agreement between radar- and ground-measured hailfall intensity, EKINPIX is related in this thesis to hail damage amounts on automobiles, buildings and cloud-to-ground (CG) lightning activity in analyzing a large number of radar-measured hail cells. The thesis consists of three parts: an introduction, three articles (submitted or published in Atmospheric Research) that are reproduced in individual chapters and a final chapter that presents two methodological approaches of how CG lightning location data could be used in the future to directly determine hailfall areas. Article 1 deals with the relationship between hailfall intensities and damages to automobiles, whereas Article 2 investigates a corresponding relationship for residential and agricultural buildings in Switzerland. Radar measurements were available from the C-band Doppler radar located at the Swiss Federal Institute of Technology (ETH) near Zurich, Switzerland. Damage claim data on automobiles were available from Winterthur Insurance (1992-1998) and several cantonal building insurance companies provided hail damage data of buildings (1992-1999). Relationships between hailfall intensity (EKINPIX) and damages to automobiles (buildings) have been analyzed for 12 (nine) hail cells with the following result: As the amount of hail damage depends strongly on the exposure and the physical characteristics of the units insured, some assumptions and simplifications were necessary. The relationship between mean damages and EKINPIX depends on the hailstorm season: high season storms (15 June-15 August) produced higher damages than low season storms vi (before and after). A seasonal difference in hailfall intensity between high and low season storm appears also from numbers and maximum hailstone diameters that were available from hailpad measurements conducted during Grossversuch IV in central Switzerland (1976-1983). The nonlinear relationships between EKINPIX and the damage variables are best described by logistic damage functions that yield correlation coefficients of 0.80. After suitable verification and calibration, logistic functions for total loss ratios (ratio between damage amounts and total sums insured) of both residential and agricultural buildings, predicted damages that are in the range of occurred losses from hailfall. Relative prediction errors for the most severe hailstorms are below 30%. The results suggest that the established logistic damage functions between radar-derived hail kinetic energy and hail damage amounts could be used by insurance companies to determine possible maximum losses (PMLs), shifting a radar-measured hail cell over a motor and/or a building portfolio of interest (e.g., over a major city). In Article 3, CG lightning measurements from Lightning Location and Tracking Systems (LPATS) of Switzerland and southern Germany are compared to determine relative detection efficiencies. CG lightning measurements of the Swiss LPATS are attributed to individual hail cells (5-min resolution), so that the entire lifecycle can be assessed and be related to radar-derived hail kinetic energy (ETH C-band Doppler radar). Analyzes of 41 hail cells that propagated over the Swiss Mittelland (1992-1995) show the following key results: Total hail kinetic energy (EKINTOT) shows good linear correspondence (correlation coefficient of 0.95) with totals of negative CG (–CG) stroke counts but reveals no direct relationship regarding positive CG (+CG) stroke totals, although hail cells were stratified according to the type of cell organization. Temporal and spatial locations of maximally expected hailfall correlate with temporal (0.88) and spatial (0.84) peaks of –CG strokes. Most hail cells (66%) show –CG stroke peaks on the average 22 min (0-65 min) and 19 km (3-58 km) prior to maximally expected hailfall. Locations of +CG stroke peaks reveal large variance relative to maximally expected hailfall. +CG strokes in weak cells tend to peak on the average 10 min before and 3.5 km after maxima in hail kinetic energy, whereas +CG stroke peaks in strong large isolated cells lag maximally expected hailfall up to 30 min and 45 km. The results of the relatively large data sample confirm the importance of the non-inductive graupel-ice charging mechanisms that explains the majority of –CG strokes at the beginning of thunderstorm development and the fact that most CG discharges are of positive polarity at mature storm phase, when an electrical charge reversal occurs in the thunderstorm with the fallout of precipitation. The spatial-temporal relationship between peaks in CG strokes and maximum hailfall intensity could be used to improve nowcasting systems of severe thunderstorms, particularly through an increase of the time of onset between CG lightning initiation and the fallout of hail. In the last chapter, the spatial relationship between patterns of –CG strokes and radar-derived hail kinetic energy is analyzed for 18 selected hail cells. Cross-correlations between lightning and energy patterns produced coefficients between 0.33 and 0.66, which are the basis for a promising approach to determine hailfall surfaces directly from lightning location data. This chapter shows two methodological approaches of how hail kinetic energy could be distributed in space, whereas the full implementation of these methods is not covered in the thesis. Once accurate methods are available, it would be possible to determine entire areas of hailfall without relying on radar data

    The Journal of Undergraduate Research: Volume 06

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    This is the complete issue of the South Dakota State University Journal of Undergraduate Research, Volume 6

    Essays on the environmental economic history of China

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    This thesis examines various aspects of the environmental economic history of China and provides the data and analysis to allow for more research at the county level. The study verifies the use of some newly developed AI based techniques, including character recognition and lexical analysis, to digitise historical information from paper sources. Applications of this newly constructed data set show that more frequent flood events will encourage rural-to-urban migration, while more frequent cold-related events will encourage urban-to-rural migration. We also adopt a Spatial Durbin Model and find that the spatial dependence of conflicts is strong. The possible mechanisms for the spillover effect of weather shocks are whether the weather shocks are spatially connected or the weather shocks encourage refugees to move to other places

    Volume 62 - Issue 3 - December, 1950

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    https://scholar.rose-hulman.edu/technic/1127/thumbnail.jp

    Quantitative risk analysis for natural hazards at local and regional scales

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    Natural hazards can have damaging consequences for human activities, causing death or economic losses. This PhD thesis concentrates on the risk of natural hazard, where risk is defined as the combination of the likelihood of a damaging event and its negative consequences. The types of hazards considered in this work are mostly geological hazards such as landslides and sinkholes, but hail is also investigated. The first part of this work focuses on the local scale, where local stands for a small group of objects, typically a few houses or a road. First, in order to improve the characterisation of the hazard, the potential of the photogrammetric method, which consists in retrieving the 3D position of objects from a set of 2D pictures, is tested. Together with this promising method, Unmanned Aerial System (UAS) are presented, since they permit to carry a camera and thus to take pictures for a photogrammetric analysis. Then, a tool to calculate the risk at local scale is presented. This tool is designed in Microsoft Excel an aims at calculating rapidly the risk using hazard maps produced according to the Swiss guidelines. A particular aspect of this model is presented in the next chapter ; it reviews the methods used to calculate the conditional probability for a falling object, such as a rock block, to impact a moving vehicle, taking into account the dimensions of the block and of the vehicles. Then, prospective aspects of such a risk model are presented and deal with the addition of multiple risk scenarios and the inclusion of uncertainty in the risk analysis using a Monte-Carlo approach. To conclude this part, a method which aims at taking the protection measures into account in the hazard maps without losing the initial hazard level is presented. The second part of this work presents risk analyses at regional scale, where the region varies from the size of a canton to the size of a (small) country. The first study concerns the risk induced by evaporite sinkholes on a building portfolio. An inventory of damaged buildings is built from different sources and projections are made to estimate the losses that the public building insurance company could face if this type of hazard was insured. Then, a stochastic model which aims at modelling shallow landslides with regard to a precipitation event, and at calculating the probability of impact with buildings is presented. It shows that the location of the landslides which occurred during the precipitation event considered in this study is positively correlated with the building location, suggesting a human influence in the landslides. To conclude this part, an analysis based on a hail event is presented and aims at relating the radar-derived maximum hailstone size reached during an event with the losses, at calculating the mean annual risk using this relation and at modelling random event to refine the risk analysis. Although the basic principles of risk analysis are relatively simple, this work highlights the diversity of the risk analyses procedure and the need to adjust the procedure to the research question. In addition, it highlights the need for good inventories of events and consequences, since these inventories are crucial to perform a good risk analysis

    High-resolution, slant-angle scene generation and validation of concealed targets in DIRSIG

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    Traditionally, synthetic imagery has been constructed to simulate images captured with low resolution, nadir-viewing sensors. Advances in sensor design have driven a need to simulate scenes not only at higher resolutions but also from oblique view angles. The primary efforts of this research include: real image capture, scene construction and modeling, and validation of the synthetic imagery in the reflective portion of the spectrum. High resolution imagery was collected of an area named MicroScene at the Rochester Institute of Technology using the Chester F. Carlson Center for Imaging Science\u27s MISI and WASP sensors using an oblique view angle. Three Humvees, the primary targets, were placed in the scene under three different levels of concealment. Following the collection, a synthetic replica of the scene was constructed and then rendered with the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model configured to recreate the scene both spatially and spectrally based on actual sensor characteristics. Finally, a validation of the synthetic imagery against the real images of MicroScene was accomplished using a combination of qualitative analysis, Gaussian maximum likelihood classification, grey-level co-occurrence matrix derived texture metrics, and the RX algorithm. The model was updated following each validation using a cyclical development approach. The purpose of this research is to provide a level of confidence in the synthetic imagery produced by DIRSIG so that it can be used to train and develop algorithms for real world concealed target detection

    Winona Daily News

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    https://openriver.winona.edu/winonadailynews/2156/thumbnail.jp

    Terrestrial environment (climatic) criteria guidelines for use in aerospace vehicle development

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    Guidelines on terrestrial environment data specifically applicable for NASA aerospace vehicles and associated equipment development are provided. The general distribution of natural environmental extremes in the conterminous United States that may be needed to specify design criteria in the transportation of space vehicle subsystems and components is considered. Atmospheric attenuation was included, since certain Earth orbital experiment missions are influenced by the Earth's atmosphere. Climatic extremes for worldwide operational needs is also included. Atmospheric chemistry, seismic criteria, and a mathematical model to predict atmospheric dispersion of aerospace engine exhaust cloud rise and growth are discussed. Atmospheric cloud phenomena are considered

    Heavy rain, hail, and tornadoes on 15 May 1968

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    Bibliography: p. 48.Enumeration continues through succeeding title
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