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

Wetterradargeräte werden mittlerweile in vielen Ländern zur Beobachtung und Messung von Hagelstürmen verwendet und liefern einen detaillierten Überblick über die Entwicklung und die Struktur von starken Gewittern. Viel Aufwand wurde in die quantitative Messung von Hagelschlägen und Kurzfristprognosen (Nowcasting) von hagelträchtigen Gewittern investiert, was für nationale Wetterdienste und Flughäfen (Warnungen), die Landwirtschaft (Hagelschutz) und Versicherungen (Schadenabschätzung und Prävention) 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 Radargeräten. Eine der besten Methoden zur Bestimmung der Hagelintensität mit Single-Polarisation Radargeräten ist die kinetische Hagelenergie, die aus der Radarreflektivität berechnet wird und das gesamte Hagelvolumen pro Fläche repräsentiert. Es hat sich gezeigt, dass die radarvermessene kinetische Hagelenergie (EKINPIX) gut mit Bodenmessungen von Hagel (Hailpads) und Hagelschäden an landwirtschaftlichen Kulturen korreliert. Aufgrund der guten Beziehung zwischen radar- und bodenvermessener Hagelintensität, wird EKINPIX in dieser Dissertation in Beziehung zu Hagelschäden an Autos, an Gebäuden und zur Häufigkeit von Wolken-Boden Blitzen (WB) gesetzt und anhand einer grossen Anzahl Hagelzellen analysiert. Die Dissertation besteht aus den folgenden drei Teilen: einer Einführung, drei wissenschaftlichen Publikationen (eingereicht oder publiziert in (Athmospheric Research) die in einzelnen Kapiteln wiedergegeben sind, und einem abschliessenden Kapitel, in dem zwei methodische Ansätze wie aus räumlichen Verteilungen von WB Blitzen gesamte Hagelflächen abgeleitet werden könnten. Artikel 1 zeigt die Beziehung zwischen Hagelintensitäten und Hagelschäden an Autos, während in Artikel 2 der Zusammenhang mit Schäden an Wohn- und Landwirtschaftsgebäuden untersucht wird. Die Radardaten stammen vom C-Band Doppler-Radar, der von der Eidgenössischen Technischen Hochschule (ETH) in der Nähe von Zürich (Schweiz) betrieben wird. Hagelschäden an Autos waren durch die Winterthur Versicherungen (1992-1998) und Hagelschäden an Gebäuden durch verschiedene Kantonale Gebäudeversicherungen (1992-1999) erhältlich. Die Beziehung zwischen Hagelintensitäten (EKINPIX) und Schäden an Autos (Gebäuden) wurden für 12 (neun) Hagelzellen analysiert, mit den folgenden Resultaten: Da das Ausmass eines Hagelschadens sehr stark vom Exposure und den physikalischen Eigenschaften der versicherten Objekte abhängt, wurden verschiedene Annahmen getroffen und Vereinfachungen eingeführt. Die Beziehung zwischen den mittleren Schäden und EKINPIX hängt von der Hagelsaison ab: Hagelzellen der Hauptsaison (15. Juni-15. August) produzierten generell höhere Schäden als Gewitter der Nebensaison (vorher und nachher). Ein saisonaler Unterschied in der Hagelintensität zeigt sich auch aus der Anzahl und der maximalen Hagelkorngrösse von Hailpad Daten, die aus dem Grossversuch IV stammen, welcher in der Zentralschweiz durchgeführt 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 für die Schadenrate (Verhältnis zwischen Schäden und Gesamtversicherungssumme) Schäden an Wohn- und Landwirtschaftsgebäuden, die in der Grössenordnung der tatsächlich vorgekommenen Schäden liegen. Der relative Fehler zwischen realen und mit den Schadenfunktionen geschätzten Schäden liegt für die stärksten Stürme unter 30%. Die erarbeiteten logistischen Schadenfunktionen zwischen radarvermessener kinetischen Hagelenergie und Hagelschäden könnten von Versicherungen zur Bestimmung von maximal möglichen Schäden (PMLs) gebraucht werden, indem eine radarvermessene Hagelzelle über ein Auto- und/oder Gebäudeportefeuille eines bestimmten Gebietes (z.B. einer grösseren Stadt) verschoben werden kann. In Artikel 3 werden WB Blitze, die von den Blitzmessnetzen der Schweiz und Süddeutschland geortet wurden, miteinander verglichen, um eine Angabe über 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 über 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 Hagelintensität korrelieren mit zeitlichen (0.88) und räumlichen (0.84) Höchstwerten in der Häufigkeit 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 Hagelintensität 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 Hagelintensität. In grossen isolierten Zellen liegt hingegen die Position der meisten +WB Blitze 30 min. und 45 km nach der höchsten Hagelintensität. Die Resultate der relativ grossen Anzahl untersuchter Gewitter bestätigen den Einfluss des nicht-induktiven Graupel-Eis Ladungsmechanismus. Dieser erklärt die Tatsache, dass die Mehrheit der –WB Blitze zu Beginn der Gewitterentwicklung vorkommen, während die meisten +WB Blitze eher am Ende der Gewittertätigkeit, während einer Umkehrung der Ladungsteilung beim Ausfall des Niederschlags, auftreten. Die zeitliche und räumliche Beziehung zwischen Höchstwerten von WB Blitzen und maximaler Hagelintensität könnte in der Zukunft für die Verbesserung der Kurzvorhersagen (Nowcasting) von starken Gewittern verwendet werden, speziell durch eine frühere Erkennung eines Hagelschlags anhand von WB-Blitz Informationen. Im letzten Kapitel wird die räumliche Beziehung zwischen Mustern von –WB Blitzen und radarvermessener kinetischer Hagelenergie für 18 ausgewählte Hagelzellen untersucht. Kreuzkorrelationen zwischen den Blitz- und Energiemuster ergeben Koeffizienten zwischen 0.33 und 0.66, was ein vielversprechender Ansatz für eine direkte Bestimmung von Hagelflächen mittels Blitzdaten ist. Zwei methodische Ansätze zur räumlichen Verteilung der Hagelenergie werden in diesem Kapitel diskutiert, wobei die vollständige Ausarbeitung der Methoden nicht mehr im Rahmen dieser Arbeit liegt. Falls dies jedoch gelingt, können Hagelflächen für 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

Gargantuan hail in Argentina

On 8 February 2018, a supercell storm produced gargantuan (>15 cm or >6 in. in maximum dimension) hail as it moved over the heavily populated city of Villa Carlos Paz in Córdoba Province, Argentina. Observations of gargantuan hail are quite rare, but the large population density here yielded numerous witnesses and social media pictures and videos from this event that document multiple large hailstones. The storm was also sampled by the newly installed operational polarimetric C-band radar in Córdoba. During the RELAMPAGO campaign, the authors interviewed local residents about their accounts of the storm and uncovered additional social media video and photographs revealing extremely large hail at multiple locations in town. This article documents the case, including the meteorological conditions supporting the storm (with the aid of a high-resolution WRF simulation), the storm's observed radar signatures, and three noteworthy hailstones observed by residents. These hailstones include a freezer-preserved 4.48-in. (11.38 cm) maximum dimension stone that was scanned with a 3D infrared laser scanner, a 7.1-in. (18 cm) maximum dimension stone, and a hailstone photogrammetrically estimated to be between 7.4 and 9.3 in. (18.8-23.7 cm) in maximum dimension, which is close to or exceeds the world record for maximum dimension. Such a well-observed case is an important step forward in understanding environments and storms that produce gargantuan hail, and ultimately how to anticipate and detect such extreme events.Fil: Kumjian, Matthew R.. State University of Pennsylvania; Estados UnidosFil: Gutierrez, Rachel. State University of Pennsylvania; Estados UnidosFil: Soderholm, Joshua S.. Universitat Bonn; AlemaniaFil: Nesbitt, Stephen William. University of Illinois at Urbana; Estados UnidosFil: Maldonado, Paula Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Luna, Lorena Medina. National Center for Atmospheric Research; Estados UnidosFil: Marquis, James. Pacific Northwest National Laboratory; Estados UnidosFil: Bowley, Kevin A.. State University of Pennsylvania; Estados UnidosFil: Alvarez Imaz, María de Los Milagros. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Salio, Paola Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentin

Experiences with >50,000 Crowdsourced Hail Reports in Switzerland

Crowdsourcing is an observational method that has gained increasing popularity in recent years. In hail research, crowdsourced reports bridge the gap between heuristically defined radar hail algorithms, which are automatic and spatially and temporally widespread, and hail sensors, which provide precise hail measurements at fewer locations. We report on experiences with and first results from a hail size reporting function in the app of the Swiss National Weather Service. App users can report the presence and size of hail by choosing a predefined size category. Since May 2015, the app has gathered >50,000 hail reports from the Swiss population. This is an unprecedented wealth of data on the presence and approximate size of hail on the ground. The reports are filtered automatically for plausibility. The filters require a minimum radar reflectivity value in a neighborhood of a report, remove duplicate reports and obviously artificial patterns, and limit the time difference between the event and the report submission time. Except for the largest size category, the filters seem to be successful. After filtering, 48% of all reports remain, which we compare against two operationally used radar hail detection and size estimation algorithms, probability of hail (POH) and maximum expected severe hail size (MESHS). The comparison suggests that POH and MESHS are defined too restrictively and that some hail events are missed by the algorithms. Although there is significant variability between size categories, we found a positive correlation between the reported hail size and the radar-based size estimates

Simulations Of Convectively-Induced Turbulence Based On Radar-Based Climatology Of Tropical Storm Types

Convective hazards such as lightning, hail, and turbulence are known to be dangerous to aviation. In order to limit aviation accidents associated with convection, the Federal Aviation Administration (FAA) has several avoidance policies in place. Though these policies have been solely based on research performed in the midlatitude, continental United States (U.S.), U.S. aviation operations in the tropics still abide by the FAA avoidance policies. In this study, a limited three year climatology of tropical convection is created using both ground-based and satellite-based radar in the Guam region in order to analyze the frequency of several storm types and to gain a sense of which storm types could most commonly influence aviation. Storm types that are classified are shallow stratiform, isolated, mesoscale convective systems, and tropical cyclones. The results of the climatology indicate that storm type most frequently present near Guam are isolated. In addition, the frequency of storms with higher echo top heights increase during the summer months, suggesting that aviation operations would be most influenced by convection during the summer. The percentage of time that the area coverage of storms exceeds the FAA avoidance policy for thunderstorm coverage also increases during the summer months. Using the Weather Research and Forecast (WRF) model, convection on August 5-6 2005 is simulated to determine the strength and extent of turbulence caused by convectively induced gravity waves. Turbulence is estimated using the Ellrod Index and indicates that Moderate-Severe turbulence is present from 10-20 km, with the greatest concentration of Moderate-Severe turbulence at 14 km throughout the entire simulation period. Further investigation of the Ellrod Index shows a dependency of turbulence strength and extent on the horizontal model resolution. The results from the model simulations are then compared to the avoidance policies set by the FAA to determine if these policies are representative of tropical convection hazards

THE APPLICATION OF SPECTRAL ANALYSIS AND ARTIFICIAL INTELLIGENCE METHODS TO WEATHER RADAR

Power spectral density (PSD) of reflectivity and polarimetric variables have the potential to provide the linkage between the dynamics and the microphysical properties of scatterers within the radar resolution volume. The artificial intelligence (AI) methods such as fuzzy logic and neural network have been widely used in weather radar. The main goal of this dissertation is to exploit spectral analysis and AI methods to the two specific areas of tornado detection and the retrieval of microphysical properties of rain-hail mixture.A novel approach of using both fuzzy logic and neural network, termed neuro-fuzzy tornado detection algorithm (NFTDA), is developed to integrate tornado's shear, spectral and polarimetric signatures for both regular resolution and high resolution with the goal of enhanced and robust detection. The spectral signatures are characterized by spectrum width and three additional parameters derived from the analysis of bispectrum, statistics, and Eigen-ratio.The statistical analysis from numerical simulation and real data has shown that NFTDA provides improved detection compared to the conventional shear-based detection algorithm in terms of probability of detection (POD), false alarm rate (FAR), and detection range. For the retrieval problem, a model of Doppler and polarimetric spectra is first developed for the presence of both raindrops and melting hail. The melting ratio is introduced the first time in the retrieval using weather radar. A genetic algorithm (GA) is introduced to solve the optimization of fitting the observed Doppler and polarimetric spectra to the model. Consequently, the drop size distribution (DSD) of both rain and hail, the melting ratio, the radial component of ambient wind and spectrum broadening can be retrieved. The retrieval algorithm is demonstrated and tested using numerical simulations

Triple-moment bulk hail microphysics scheme to investigate the sensitivities of hail to aerosols, A

2012 Spring.Includes bibliographical references.Hail is a frequent occurrence in warm season deep convection in many mid-latitude regions and causes significant damage to property and agricultural interests every year. Hail can also have a substantial impact on the precipitation characteristics of deep convection as well as on the dynamic and thermodynamic properties of convective downdrafts and cold-pools, which in turn can affect storm evolution and propagation. In addition, large and often destructive hail commonly occurs in severe convection, yet most one- (1M) and two-moment (2M) bulk microphysics schemes in cloud-resolving numerical models are incapable of producing large hail (diameter D ≥ 2 cm). The limits imposed by fixing one or two of the distribution parameters in these schemes often lead to particularly poor representations of particles within the tails of size distribution spectra; an especially important consideration for hail, which covers a broad range of sizes in nature. In order to improve the representation of hail distributions in simulations of deep moist convection in a cloud-resolving numerical model, a new triple-moment bulk hail microphysics scheme (3MHAIL) is presented and evaluated. The 3MHAIL scheme predicts the relative dispersion parameter for a gamma distribution function via the prediction of the sixth moment (related to the reflectivity factor) of the distribution in addition to the mass mixing ratio and number concentration (third and zeroeth moments, respectively) thereby allowing for a fully prognostic distribution function. Initial testing of this scheme reveals significant improvement in the representation of sedimentation, melting, and formation processes of hail compared to lower-order moment schemes. The 3MHAIL scheme is verified in simulations of a well-observed supercell storm that occurred over northwest Kansas on 29 June 2000 during the Severe Thunderstorm and Electrification and Precipitation Study (STEPS). Comparisons of the simulation results with the observations for this case, as well as with results of simulations using two different 2M microphysics schemes, suggest a significant improvement of the simulated storm structure and evolution is achieved with the 3MHAIL scheme. The generation of large hail and subsequent fallout in the simulation using 3MHAIL microphysics show particularly good agreement with surface hail reports for this storm as well as with previous studies of hail in supercell storms. On the other hand, the simulation with 2M microphysics produces only small hail aloft and virtually no hail at the surface, whereas a two-moment version of the 3MHAIL scheme (with a fixed relative dispersion parameter) produces unrealistically high amounts of large hail at low levels as a result of artificial shifts in the hail size spectra towards larger diameter hail during the melting process. The 3MHAIL scheme is also used to investigate the impact of changing the concentrations of aerosols that act as cloud condensation nuclei (CCN) on hail for the 29 June 2000 supercell case. For the simulated supercells in the particular environment examined, an increase in CCN from 100 to 3000 cm-3 leads to an increase in the numbers and a decrease in the sizes of cloud droplets, as expected, yet the overall storm dynamics and evolution are largely unaffected. Increases in CCN lead to non-monotonic responses in the bulk characteristics of nearly all hydrometeor fields, surface precipitation, and cold-pool strength. However, higher concentrations of CCN also result in larger hail sizes and greater amounts of large diameter (≥ 2 cm) hail both aloft as well as at the surface. Analyses of the hail formation and growth mechanisms for these simulations suggest that the combination of increased sizes of new hail particles and localized reductions in numbers of new hailstones forming near maximum growth regions with increasing CCN tends to promote conditions that lead to increased hail sizes and amounts of large hail

Computational Electromagnetics Applied to Scattering Observed by Polarimetric Weather Radar

The primary topics of this dissertation are issues existing in the current ensemble scattering procedures. These procedures are failing to quantitatively reproduce polarimetric signatures from resolution volumes filled with ensembles of resonant size precipitation, biota, and anthropogenic scatterers. Sources of these failures are traced to the constraints on the topology that is admissible to the different modeling procedures. The dissertation evaluates in a systematic manner the current modeling procedures focusing on limitation sources and their effects on the overall process of polarimetric variable simulation. It re-evaluates limitations of the widely used T-Matrix approach and discusses sources of instability. Based on the identified limitations, a novel computational electromagnetics (CEM) approach to scatterer modeling and polarimetric variable calculation is introduced to mitigate the current limitations. Detailed overview of the process as well as guidance on applying the CEM to the polarimetric variable calculation is presented. This is the first systematic exploration of a specific CEM solver to modeling of polarimetric radar signatures from precipitation and biota. Finally, to demonstrate meteorological application the CEM approach is evaluated by comparison with some polarimetric radar observations of hail. Of main significance is modeling of large and giant hail having surface protuberances, or rough, irregular shape. Additionally, radar observations of biota and radar cross section (RCS) measurements are considered for aeroecology applications. As an example, the precise size and shape model of Brazilian Free-tailed bat (Tadarida brasiliensis) is created and compared to the RCS measurements, as well as to radar observations of bat emergence in Texas plains

Radar-based assessment of hail frequency in Europe

In this study we present a unique 10 year climatology of severe convective storm tracks for a large European area covering Germany, France, Belgium and Luxembourg. For the period 2005–2014, a high-resolution hail potential composite of 1×1 km$^{2}$ is produced from two-dimensional radar reflectivity and lightning data. Individual hailstorm tracks as well as their physical properties, such as radar reflectivity along the tracks, were reconstructed for the entire time period using the Convective Cell Tracking Algorithm (CCTA2D). A sea-to-continent gradient in the number of hail days per year is found to be present over the whole domain. In addition, the highest number of severe storms is found on the leeward side of low mountain ranges such as the Massif Central in France and the Swabian Jura in southwest Germany. A latitude shift in the hail peak month is observed between the northern part of Germany, where hail occurs most frequently in August, and southern France, where the maximum amount of hail is 2 months earlier. The longest footprints with high reflectivity values occurred on 9 June 2014 and on 28 July 2013 with lengths reaching up to 500 km. Both events were associated with hailstones measuring up to 10 cm diameter, which caused damage in excess of EUR 2 billion

SYNOPTIC AND MESOSCALE ANALYSIS OF HAILSTORMS OVER CROATIA ON 22 AND 23 JUNE 2007

A case of severe convective development affecting Croatia on 22 and 23 June 2007 is analyzed by means of synoptic material, satellite, radar and lightning data as well as hailpad data and hail observations. The development occurred during the passage of a cold front in strong upper-level south-westerly flow, bringing warm and humid air from the West Mediterranean. The onset of convection was triggered by the orographic lifting on the islands and later on the Dinaric Alps. A supercell developing in the North Adriatic split into two cells due to strong vertical wind shear and veering of the wind in the lowest 3 km. The right-moving cell with cyclonic rotation was longer living and the left one died out. Large hail was reported along the path of the cell. Later on, convective cells developing over the continental part of Croatia were of lower intensity, but still bringing hail of the hazelnut size. Hailpad measurements and hail observations show the distribution of hail in time and give the information about the sizes of hailstones. Aladin meso-scale model performance is tested for the development in the North Adriatic, showing that the model could successfully reproduce the environment and the conditions for severe convective development, however underestimating the precipitation amount