It is shown that in the simultaneous dual-polarization radar mode, the differential phase (<inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>) between the orthogonally ...polarized waves impinging on hail affects the polarimetric variables. This effect is caused by interference of the polarized waves scattered by nonspherical particles. The <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula> impact is considered for dry hail and water-coated hailstones. For the hailstones' canting angles oriented uniformly relative to the vertical, reflectivity and differential reflectivity do not depend on <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>, but the correlation coefficient between the polarized waves and phase upon scattering do. Tumbling of falling hailstones is considered using the Fisher distribution of the orientation angles. It is shown that the <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula> impact enhances with increasing tumbling. The <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula> impact should be considered in hail detection methods utilizing the correlation coefficient. The potential of using the differential phase upon scattering in hail detection and sizing is also discussed.
Large hail is a primary contributor to damages and loss around the world, in both agriculture and infrastructure. The sensitivity of passive microwave radiometer measurements to scattering by hail ...led to the development of proxies for severe hail, most of which use brightness temperature thresholds from 37-GHz and higher-frequency microwave channels on board weather satellites in low-Earth orbit. Using 16+ years of data from the Tropical Rainfall Measuring Mission (TRMM; 36°S–36°N), we pair TRMM brightness temperature–derived precipitation features with surface hail reports in the United States to train a hail retrieval on passive microwave data from the 10-, 19-, 37-, and 85-GHz channels based on probability curves fit to the microwave data. We then apply this hail retrieval to features in the Global Precipitation Measurement (GPM) domain (from 69°S to 69°N) to develop a nearly global passive microwave–based climatology of hail. The extended domain of the GPM satellite into higher latitudes requires filtering out features that we believe are over icy and snowy surface regimes. We also normalize brightness temperature depression by tropopause height in an effort to account for differences in storm depth between the tropics and higher latitudes. Our results show the highest hail frequencies in the region of northern Argentina through Paraguay, Uruguay, and southern Brazil; the central United States; and a swath of Africa just south of the Sahel. Smaller hot spots include Pakistan, eastern India, and Bangladesh. A notable difference between these results and many prior satellite-based studies is that central Africa, while still active in our climatology, does not rival the aforementioned regions in retrieved hailstorm frequency.
Climatology of hail in Argentina Mezher, Romina N.; Doyle, Moira; Barros, Vicente
Atmospheric research,
10/2012, Letnik:
114-115
Journal Article
Recenzirano
Odprti dostop
The annual cycle, annual and seasonal frequency and geographical distribution of hail in Argentina during the 1960–2008 period are examined. Eight regions covering the whole territory were defined ...based on the correlation of the mean annual hail frequency between all weather stations. Regions lying between 30° and 40°S as well as those dominated by mountains present the highest hail frequencies in Argentina. The eastern and coastal areas of the country experience hail events mainly during springtime but they may start in late winter and continue through the beginning of summer. Events in western and central Argentina also predominate in spring but the maximum frequencies are observed during summer months. Trends in the annual number of hail events calculated for each region indicate that events in northwestern and northeastern Argentina have been increasing as well as in southern Patagonia. On the other hand, in central Argentina, southern Buenos Aires–La Pampa, northern Buenos Aires–Litoral and northern Patagonia trends are negative and statistically significant in the first two regions, basically by the decrease of events during spring and summer.
► We examined annual and seasonal hail frequency in Argentina in the 1960–2008 period ► We analyzed hail events' geographical and temporal distribution ► We calculated trend in hail frequency for eight different regions of Argentina ► Negative trends are accompanied by rise of the freezing level height
Armed with a pocketknife, rope, and calf jack, she created an anchor point in the exposed mass and eventually removed the deformed body. In the interim, Mama and I were trying our best at babysitting ...but eventually had to send a Hail Mary distress message as the boys were becoming too rambunctious for a 75-year-old woman who had just had cataract surgery and my essentially useless right shoulder with a torn rotator cuff. About that time, she and Brant rolled in with the prolapsed cow, unloaded and situated her and then retrieved the boys for desperately needed naps before their scheduled appearance at a neighbor’s birthday party.
At the end of July 2013, a series of severe thunderstorms associated with heavy rainfall, severe wind gusts and large hail affected parts of Germany. On 28 July 2013, two supercells formed almost ...simultaneously in southern Germany, from which only the more southerly cell produced hailstones up to 10 cm in diameter on a hailswath approximately 120 km long and 15–20 km wide. For the insurance industry, this event, with losses of more than EUR 1 billion, was one of the most expensive natural disasters that has ever occurred in Germany.
This article investigates the creation, temporal evolution and effects of the most severe supercell that day by considering and merging radar and satellite data, eyewitness reports, insurance loss data and numerical model studies. Observations of hail at ground level fit very well with a cold‐ring‐shaped structure in the cloud‐top brightness temperature observed by a geostationary satellite imager. Various simulations conducted with the convection‐permitting COnsortium for Small‐scale MOdeling (COSMO) revealed that the track of the hailstorm could be reproduced only when convection was triggered artificially by two warm bubbles that produced single cells that were precursors of the supercell. The model results suggested that the supercell developed near a pre‐existing single cell through low‐level flow convergence in an environment with moderate CAPE but substantial wind shear and storm‐relative helicity, both of which persisted for several hours in the area in which the supercell moved.
On 28 July 2013, two supercells formed almost simultaneously in southern Germany, from which only the more southerly cell produced hailstones up to 10 cm in diameter on a hailswath approximately 120 km long and 15–20 km wide (see figure, with radar reflectivity in green and ESWD hail reports as red triangles). This article investigates the creation and temporal evolution of the most severe supercell by considering various observational data and numerical model studies. Radar observations suggest that the supercells developed from two pre‐existing single cells, while simulations with the convection‐permitting COSMO model reveal that the hailstorm could be reproduced only when convection is triggered artificially by warm bubbles.
•The contact time between hail and membrane is related to the membrane stiffness and impact velocity.•The resistance to external loads is not only related to the pretension but also the rise-span ...ratio.•The relaxation effect due to the hail may significantly reduce the critical wind speed of membrane.
In this paper, the dynamic response of a typical four-point pretensioned saddle membrane structure under hail impact load is investigated by numerical simulations and experimental studies. Firstly, the initial shape of saddle membrane is obtained by form-finding analysis using the finite element analysis software ANSYS. The complex mechanical process of hail impact on the flexible membrane is simulated by LS-DYNA/Explicit dynamic analysis program, and the dynamic response of membrane, including displacement, velocity and acceleration, etc, is characterized. Then the experiment of saddle membrane under hail impact is carried out by applying the same loading conditions with the numerical analysis. The comparison between the numerical and experimental results shows good agreement, which verifies the reliability of the numerical simulations. It is discovered that the pretension relaxation induced by the hail impact may decrease the critical wind speed of membrane, and significantly increase the risk of membrane instability subject to hailstorm. Finally, the dynamic characteristics of typical four-point tensioned saddle membrane are summarized, which may provide reference for the design, construction and maintenance of membrane structures.
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.
Abstract
Data from a dual-polarized, solid-state X-band radar and an operational C-band weather radar are used for high-resolution analyses of two hailstorms in the Vienna, Austria, region. The ...combination of both radars provides rapid-update (1 min) polarimetric data paired with wind field data of a dual-Doppler analysis. This is the first time that such an advanced setup is used to examine severe storm dynamics at the eastern Alpine fringe, where the influence of local topography is particularly challenging for thunderstorm prediction. We investigate two storms transitioning from the pre-Alps into the Vienna basin with different characteristics: 1) A rapidly evolving multicell storm producing large hail (5 cm), with observations of an intense
Z
DR
column preceding hail formation and the rapid development of multiple pulses of hail; and 2) a cold pool–driven squall line with small hail, for which we find that the updraft location inhibited the formation of larger hailstones. For both cases, we analyzed the evolution of different
Z
DR
column metrics as well as updraft speed and size and found that (i) the 90th percentile of
Z
DR
within the
Z
DR
column was highest for the cell later producing large hail, (ii) the peak 90th percentile of
Z
DR
preceded large hailfall by 20 min and highest updraft size and speed by 10 min, and (iii) sudden drops of the 90th percentile of
Z
H
within the
Z
DR
column indicated imminent hailfall.
Significance Statement
Thunderstorm evolution on the transition from complex terrain into the Vienna basin in northeastern Austria varies strongly. In some instances, thunderstorm cells intensify once they reach flat terrain, while in most cases there is a weakening tendency. To improve our process understanding and short-term forecasting methods, we analyze two representative cases of hail-bearing storms transitioning into the Vienna basin. We mainly build our study on data from a new, cost-efficient weather radar, complemented by an operational radar, lightning observations, and ground reports. Our results show which radar variables could be well suited for early detection of intensification, and how they relate to thunderstorm updraft speeds and lightning activity.
•Causes of dust settlement of the surface of PV module.•Impact of dust settlement on the thermal, optical and electrical characteristics of the PV module.•Impact of the hail storm on the PV ...module.•Study of different types of mitigation techniques.
The power sector has been facing the problems of the continuous increase in demand and lack of sufficient generation of electric energy using fossil fuels. The environmental problems (pollution and global warming), the continuously increasing cost of fossil fuels and the shortage of fossil fuels are mainly concerned to harvest energy from sustainable and clean sources. One of the promising sustainable energy sources is solar energy. Electrical energy can be produced from solar radiation by using the photovoltaic system. Though, power generation from PV solar system is not yet viable because of its low efficiency. Apart from low efficiency, other factors, especially environmental factors such as dust, hail, humidity and temperature and installation elements such as tilt angle, installation site, and altitude influence the performance of the PV module. This study reviews the currently available works on the subject of causes of dust deposition on the surface of the PV module, the impact of dust settlement on the electrical, optical and thermal characteristics of PV module. This paper also synthesizes current understanding of the effect of the hailstorm on the PV module and provides a prospectus for future research on this topic. A protecting system for the PV module from the hailstorm is needed to develop. The current review also summarizes the past, present studies of different types of mitigation technique so that it can be helpful in choosing the most suitable method for dust cleaning.
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