Severe Hailstorms Research Articles

Characteristics of cloud-to-ground lightning activity in hailstorms over Yunnan province

The characteristics of cloud-to-ground (CG) lightning for nine hailstorms in Yunnan province of China are analyzed statistically. It is determined that the hailstorms were found to present dominant negative CG lightning flashes at any given stage. One specific hailstorm occurring on July 16, 2006, is analyzed in detail by using the data from a CG lightning location network and Doppler radar. This severe hailstorm, which exhibited strong vertical development with cloud tops reaching 15.9km, produced hailstones as large as 15mm and had a lifespan of 3h and 12min. The total CG lightning within the hailstorm showed high levels of activity with flash rates of up to 79fl/5min. The analysis of the storm cell’s lifecycle shows similar trends between the CG lightning flash rates and radar-derived parameters. Cloud-to-ground flashes tended to initiate within the cloud region with reflectivity of more than 30 dBZ at the −10°C isotherm height. A distinct increase in CG flash rate is shown during the rapid development stages of hailstorms. The CG lightning jump pattern appears to be an effective tool for short-term forecasting of possible occurrences of severe weather.

Assessment of severe hailstorms and hail risk using weather radar data

ABSTRACTSevere storms that produce hail of significant amount or size carry a high risk, being responsible for damage at the ground. Hail spawned from these storms can affect crops, automobiles and buildings. A total of 52 hail events that occurred in May 2013 in southern Romania are used to investigate the relation between radar‐derived products and damage produced by hail. Two case studies are also presented to highlight the methodology used in this study.Three‐dimensional single polarization weather radar data were used to derive composite reflectivity, echo top heights, vertically integrated liquid, vertically integrated liquid density and hail kinetic energy flux to detect the hail clouds. Time integration and spatial distribution of these radar products were produced in order to capture the swath, intensity and longevity of the hailstorms. Hail and damage reports were used to link the radar variables to the effects of hailstorms at the ground. Hail size information was arbitrarily broken down into bins of reported hail to investigate the relation between hail size and radar parameters. The results show that the areas where hail and damage were reported are well captured by the footprints and magnitude of the radar variables. The average values of the radar parameters corresponding to hail size bins increase with the increase of hail diameter. A steeper increasing trend characterizes the vertically integrated liquid density and hail kinetic energy flux. The results show a good agreement between weather radar data and surface reports.

FIELD PERFORMANCE OF ASIAN PEAR CULTIVARS IN THE HOT, HUMID SUMMER CONDITIONS OF THE MID-ATLANTIC REGION OF THE UNITED STATES

Production of European pears (Pyrus communis L.) in the eastern United States is limited by a number of physiological and pathological problems. In an attempt to expand sustainable pear production in that region, a series of long-term field trials of Asian pear [Pyrus pyrifolia (Burm. F) Nak. {syn. P. serotine L.}] were established at two sites in Maryland. To compare precocity, productivity and survival, nine Asian pear cultivars and three European cultivars were planted in 2010 at the Wye Research and Education Center. Asian pears were precocious and productive and many trees flowered and fruited in the second leaf. After the fourth leaf, survival of ‘Isi’iwasi’, ‘Shinsui’, ‘Kosui’ and ‘Olympic’ was good. Many ‘Hosui’ and ‘Ya Li’ (Asian pear) trees as well as ‘Bartlett’ and ‘Golden Russett’ (European pear) trees had died at that point, following bloom infections of fire blight (Erwinia amylovora). Eighteen pear cultivars in two established plantings were evaluated for their field-tolerance to fire blight following a severe hailstorm at Keedysville. The cultivars ‘Shin Li’, ‘Daisu Li’, ‘Shinsui’ and ‘Olympic’ fared as well as ‘Magness’, a fire blight-tolerant European pear that served as a benchmark in that evaluation. On the other hand, ‘Hosui’, ‘Choju’, ‘Kosui’, ‘Seigyoku’, ‘Ya Li’ and ‘Ts’e Li’ were severely damaged. Using fruit from the replicated trial at Wye, consumer tastings were also conducted. In these tastings, ‘Yoinashi’, ‘Atago’, ‘Shinko’ and ‘Olympic’ were well-received by consumers. After tasting Asian pears, most people reported that they would be interested in purchasing the fruit and asked for the names of local producers, even those less familiar with the crop. Based on our long-term research results, there appears to be a good potential for locally-produced Asian pear fruit. With the correct cultivar selection for fire blight management, local growers should be able to produce this alternative crop sustainably and market their fruit profitably.

Sequential Disturbance Effects of Hailstorm and Fire on Vegetation in a Mediterranean-Type Ecosystem

Frequency and intensity of disturbance is projected to increase for many ecosystems globally, with uncertain consequences, particularly when disturbances occur in rapid succession. We quantified community response (52 shrub species and the tree Eucalyptus todtiana) to a severe hailstorm followed 2 months later by prescribed fire for a Mediterranean-type shrubland in southwestern Australia. Partial overlap of hailstorm path and fire perimeter provided a unique opportunity to compare storm and fire effects along a storm severity gradient (high–moderate–none) with and without fire. We quantified disturbance severity (bark and canopy removal, scorch height) and subsequent response (resprouting type, quantity and quality, and seedling regeneration) to evaluate evidence for disturbance interactions and implications for ecosystem recovery. Canopy loss, litter deposition, and tree bark removal increased significantly with hailstorm severity. Scorch heights in hailstorm + burn were significantly higher than fire alone, suggesting one disturbance conditioned the effect of the next. Hailstorm severity interacted with fire such that severely storm-affected shrubs and trees displayed reduced resprouting quantity and quality (length) after fire, implying resource depletion. Seedling regeneration was highest in fire-only plots for soil-stored seed species, while for serotinous species it was significantly reduced by the combination of storm and fire. Overall, our results show strong resilience of this Mediterranean-type ecosystem to storm or fire alone, whereas successive storm and fire reduced resprouting quantity and quality and selectively filtered recruitment of serotinous species, potentially altering species composition and structure. These results underscore the complex effects of linked and compound disturbances and reveal an important knowledge gap requiring future research.

Matching methods of classic hail echo cores of weather radar

Because the shape, intensity, and texture features of classic hail echo cores are easy to observe, these features are used to examine the matching methods of classic hail echo cores by using template-based and feature-based matching algorithms in this study. We first introduce the shape, intensity, and texture features of classic hail echo cores and the methods of expressing them quantitatively. Template-based and content-based matching algorithms are then used to calculate the similarity distance between classic hail echoes and real-time echoes and to determine the matching patterns between them based on pixels and features. In addition, we verify and analyze the proposed matching methods by using the case data of an extraordinarily severe hailstorm occurring in the Gansu province of China on May 30, 2005. Our research indicates that the identification rates of these two types of matching methods are very high and that the color features of classic hail echo core images are easy to observe. Moreover, V-shaped notches can also be identified and matched by using the texture feature-based matching method under stricter conditions. However, the results rely to a certain degree on the choices of templates, which indicate that the texture features of classic hail echo core images are not very obvious.

Gap-filling strategies for annual VOC flux data sets

Abstract. Up to now the limited knowledge about the exchange of volatile organic compounds (VOCs) between the biosphere and the atmosphere is one of the factors which hinders more accurate climate predictions. Complete long-term flux data sets of several VOCs to quantify the annual exchange and validate recent VOC models are basically not available. In combination with long-term VOC flux measurements the application of gap-filling routines is inevitable in order to replace missing data and make an important step towards a better understanding of the VOC ecosystem–atmosphere exchange on longer timescales. We performed VOC flux measurements above a mountain meadow in Austria during two complete growing seasons (from snowmelt in spring to snow reestablishment in late autumn) and used this data set to test the performance of four different gap-filling routines, mean diurnal variation (MDV), mean gliding window (MGW), look-up tables (LUT) and linear interpolation (LIP), in terms of their ability to replace missing flux data in order to obtain reliable VOC sums. According to our findings the MDV routine was outstanding with regard to the minimization of the gap-filling error for both years and all quantified VOCs. The other gap-filling routines, which performed gap-filling on 24 h average values, introduced considerably larger uncertainties. The error which was introduced by the application of the different filling routines increased linearly with the number of data gaps. Although average VOC fluxes measured during the winter period (complete snow coverage) were close to zero, these were highly variable and the filling of the winter period resulted in considerably higher uncertainties compared to the application of gap-filling during the measurement period. The annual patterns of the overall cumulative fluxes for the quantified VOCs showed a completely different behaviour in 2009, which was an exceptional year due to the occurrence of a severe hailstorm, compared to 2011. Methanol was the compound which, at 381.5 mg C m−2 and 449.9 mg C m−2, contributed most to the cumulative VOC carbon emissions in 2009 and 2011, respectively. In contrast to methanol emissions, however, considerable amounts of monoterpenes (−327.3 mg C m−2) were deposited onto the mountain meadow during 2009 caused by a hailstorm. Other quantified VOCs had considerably lower influences on the annual patterns.

Undisturbed and disturbed above canopy ponderosa pine emissions: PTR-TOF-MS measurements and MEGAN 2.1 model results

Abstract. We present the first eddy covariance flux measurements of volatile organic compounds (VOCs) using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) above a ponderosa pine forest in Colorado, USA. The high mass resolution of the PTR-TOF-MS enabled the identification of chemical sum formulas. During a 30 day measurement period in August and September 2010, 649 different ion mass peaks were detected in the ambient air mass spectrum (including primary ions and mass calibration compounds). Eddy covariance with the vertical wind speed was calculated for all ion mass peaks. On a typical day, 17 ion mass peaks, including protonated parent compounds, their fragments and isotopes as well as VOC-H+-water clusters, showed a significant flux with daytime average emissions above a reliable flux threshold of 0.1 mg compound m−2 h−1. These ion mass peaks could be assigned to seven compound classes. The main flux contributions during daytime (10:00–18:00 LT) are attributed to the sum of 2-methyl-3-buten-2-ol (MBO) and isoprene (50%), methanol (12%), the sum of acetic acid and glycolaldehyde (10%) and the sum of monoterpenes (10%). The total MBO + isoprene flux was composed of 10% isoprene and 90% MBO. There was good agreement between the light- and temperature dependency of the sum of MBO and isoprene observed for this work and those of earlier studies. The above canopy flux measurements of the sum of MBO and isoprene and the sum of monoterpenes were compared to emissions calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN 2.1). The best agreement between MEGAN 2.1 and measurements was reached using emission factors determined from site-specific leaf cuvette measurements. While the modeled and measured MBO + isoprene fluxes agree well, the emissions of the sum of monoterpenes is underestimated by MEGAN 2.1. This is expected as some factors impacting monoterpene emissions, such as physical damage of needles and branches due to storms, are not included in MEGAN 2.1. After a severe hailstorm event, 22 ion mass peaks (attributed to six compound classes plus some unknown compounds) showed an elevated flux for the two following days. The sum of monoterpene emissions was 4–23 times higher compared to emissions prior to the hailstorm while MBO emissions remained unchanged. The monoterpene emission (in mg compound m−2) during this measurement period is underestimated by 40% if the effect of this disturbance source is not considered.

A severe hailstorm across the English Midlands on 28 June 2012

WeatherVolume 68, Issue 11 p. 284-291 Research Article A severe hailstorm across the English Midlands on 28 June 2012 Matthew R. Clark, Matthew R. Clark Met Office, Exeter Tornado and Storm Research Organisation, OxfordSearch for more papers by this authorJonathan D. C. Webb, Corresponding Author Jonathan D. C. Webb Tornado and Storm Research Organisation, OxfordCorrespondence to: J. D. Webb [email protected]Search for more papers by this author Matthew R. Clark, Matthew R. Clark Met Office, Exeter Tornado and Storm Research Organisation, OxfordSearch for more papers by this authorJonathan D. C. Webb, Corresponding Author Jonathan D. C. Webb Tornado and Storm Research Organisation, OxfordCorrespondence to: J. D. Webb [email protected]Search for more papers by this author First published: 28 October 2013 https://doi.org/10.1002/wea.2162Citations: 17Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume68, Issue11November 2013Pages 284-291 RelatedInformation

Extreme hail day climatology in Southwestern France

The concentration of hail damage over a very few days of each warm season is a main characteristic of hail climatology in Southwestern France. The hailpad networks set up there in 1988 by the ANELFA hail prevention project have allowed the development of a new extreme hail day climatology which consists in examining the hail day data in the Atlantic region mainly under maritime conditions, and in the Pyrenean region, under continental and mountain influences. A pyramidal representation of each daily mean hailfall parameter (frequency per station, kinetic energy per hailfall, and kinetic energy per station), ranked by order of magnitude, allows a comparison of the mean and extreme values in the two regions, and reveals the strongest hail days in each one. During the 23-year period under study, 13 extreme situations (7 in the Atlantic region, 6 in the Pyrenean one) are highlighted, keeping the first three day ranking for each parameter. For each day, the synoptic situation, cell type, storm trajectories, and hail damages are examined, and numerical simulations with the WRF model, initialized by the CDAS/NCEP-NCAR reanalysis program, are considered.The study confirms that the Pyrenean region (20,000km2) has experienced the major hail situations, with record values of each parameter for the two regions. On the frequency record day (16 April 2007), 17% of the hailpad stations were impacted, and on the kinetic energy record day (16 July 2009), the total hailstone energy reached 33J/m2 per station. Two main types of synoptic situations have been identified according to the location of the pressure low generating the upper level flow, either near Portugal or near Ireland. A third type, with the pressure low above the Mediterranean, has been observed only once. The WRF-NMM simulations show that all the severe hailstorms that occurred in the twelve situations (one situation is common to both regions) developed in the areas where the mesoscale environment was characterized by a strong dynamical forcing and by high values of the low-level and deep shears. After calibration with this sample of extreme hail days, the WRF model appears promising for severe hail forecasting.

Impacto de uma tempestade de granizo em diferentes táxons vegetais: queda foliar em um ambiente de montanha

Natural catastrophes in the planet increased over 400% from 1970 to 2005, causing severe impact on natural ecosystems, and are sought to increase in the forthcoming decades due to climate change driven events. However, the descriptions of the impacts caused by events as hailstorms on wild ecosystems are anecdotal in the tropical region. The occurrence of a severe hailstorm on a mountainous tropical environment in Brazil allowed, for the first time, to examine hailstorm impact on 32 plant species belonging to distinct families. The study was carried out in an area of rupestrian field located in Serra do Cipo, Minas Gerais State, Brazil. The impact of hail on the vegetation was evaluated by an index of damage and the damage level was related to plant species architectural features. Hail impact differed strongly among the species and was influenced by plant height, growth form, leaf traits and stem type. Hailstorms are natural disturbance phenomena that have differential impacts on plants species in rupestrian fields. Key words: climate change, hailstorm damage, plant resistance, rupestrian fields, Serra do Cipo.

Toward a Global Climatology of Severe Hailstorms as Estimated by Satellite Passive Microwave Imagers

AbstractAn 8-yr climatology of storms producing large hail is estimated from satellite measurements using Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). This allows a unique, consistent comparison between regions that cannot be consistently compared using ground-based records because of varying data collection standards. Severe hailstorms are indicated most often in a broad region of northern Argentina and southern Paraguay and a smaller region in Bangladesh and eastern India. Numerous hailstorms are also estimated in the central and southeastern United States, northern Pakistan and northwestern India, central and western Africa, and southeastern Africa (and adjacent waters). Fewer hailstorms are estimated for other regions over land and scattered across subtropical oceans. Very few are estimated in the deep tropics other than in Africa. Most continental regions show seasonality with hailstorms peaking in late spring or summer. The South Asian monsoon alters the hailstorm climatology around the Indian subcontinent. About 75% of the hailstorms on the eastern side (around Bangladesh) occur from April through June, generally before monsoon onset. Activity shifts northwest to northern India in late June and July. An arc along the foothills in northern Pakistan becomes particularly active from mid-June through mid-August. The AMSR-E measurements are limited to early afternoon and late night. Tropical Rainfall Measuring Mission (TRMM) measurements are used to investigate diurnal variability in the tropics and subtropics. All of the prominent regions have hailstorm peaks in late afternoon and early evening. The United States and central Africa have the fewest overnight and early morning storms, while subtropical South America and Bangladesh have the most.

Hail impact on leaves and endophytes of the endemic threatened Coccoloba cereifera (Polygonaceae)

There is increasing evidence that some natural disturbances are increasing in frequency and intensity with global change, but the effects of these changes on plant populations is poorly understood. It is estimated that for every 1°C increase in the summer mean minimum temperature, there is a 40% increase in hail damage. Severe hailstorms can cause large impacts on biological communities. In 2008, a strong hailstorm hit the speciose and endemic rupestrian vegetation in Serra do Cipo, Brazil. This event prompted us to record its effects on the narrowly distributed and threatened species Coccoloba cereifera (Polygonaceae). About 33 to 60% of the leaves on the 246 individuals surveyed were lost. The disturbance also influenced some of the physiological traits of C. cereifera, increasing the concentration of photosynthetic pigments (chlorophyll and carotenoid) and polyphenols in the leaves. The most pronounced increase of chlorophyll was in young leaves (ca. 60%). Carotenoid content increased by ca. 50% in all leaf ages, while polyphenols increased tenfold. Contrarily, the endophyte richness decreased drastically after the event (from 104 to 33 species), only 12% of similar species remain. The hail storm strongly influenced all variables evaluated in this study, i.e., structure, physiology, and associated fungi. These results show that hailstorm had a dramatic and immediate impact on C. cereifera and may also severely affect other endemic or threatened plant species. Therefore, it is imperative that we broaden our knowledge on global climate change impacts for the conservation of native species.

Severe hailstorms near Southern Andes in the presence of mountain waves

Experimental satellite and radar data and numerical simulations at constant pressure levels were analyzed to estimate the relative importance of mountain waves during the development of 3 severe deep convection events with abundant hail precipitation in Mendoza, Argentina. The mesoscale numerical simulation model WRF 3.0 was used to determine the regional circulation previous to the deep convection. GPS radio occultation data were used to validate the simulations. It was found that updrafts generated by mountain waves constitute a possible triggering mechanism during the storms initiation. A continuous wavelet transform analysis was applied to the vertical velocity. In all cases, large amplitude stationary waves were observed just before the initiation of convection, possibly triggering it. The horizontal direction of propagation and the corresponding horizontal and vertical wavelengths of both main modes were identified. Vertical velocity and convective inhibition index were found to be potential storm forecasting flags in this region.

The impact of two extreme weather events and other causes of death on Carnaby’s Black Cockatoo: a promise of things to come for a threatened species?

Carnaby’s Black Cockatoo is an endangered species which has undergone a dramatic decline in range and abundance in southwestern Australia. Between October 2009 and March 2010 the species was subjected to a possible outbreak of disease in one of its major breeding areas and exposed to an extremely hot day and a severe localized hail storm. In addition, collisions with motor vehicles are becoming an increasing threat to the species. All of these stochastic events resulted in many fatalities. Species such as Carnaby’s Black Cockatoo which form large flocks are particularly susceptible to localized events such as hail storms, contagious disease and collisions with motor vehicles. Extreme temperatures may have major impacts on both flocking and non-flocking species. Predictions of climate change in the southwest of Western Australia are that there will be an increased frequency of extreme weather events such as heat waves and severe hail storms. The implications of more events of this nature on Carnaby’s Black Cockatoo are discussed.

Effects of Natural Hail Damage on Ear Rots, Mycotoxins, and Grain Quality Characteristics of Corn

In 2009, two severe hail storms affected more than 400,000 ha of corn (Zea mays L.) during early reproductive stages (R1 to R3) in Iowa. Concerns were raised regarding marketability, increased ear rot disease, and associated mycotoxin contamination. To address these concerns, ear samples were collected within 48 h of combine harvest from 56 fields damaged by hail and 27 undamaged fields. Ears were visually assessed for kernel damage and ear rot severity. After shelling, test weight, moisture, protein, oil, starch, and density were determined before grain was ground and tested for deoxynivalenol (DON), zearalenone, and fumonisins using commercially available antibody‐based lateral flow strip tests. Confirmation analyses on elevated samples was performed by gas chromatography for DON and high pressure liquid chromatography for zearalenone and fumonisin. Fusarium, Gibberella, and Cladosporium ear rots were the most prevalent diseases. Hail damage to kernels increased the risk of ear rot and mycotoxin contamination. The most prevalent mycotoxin detected was DON (mean 2.63 mg kg−1), followed by zearalenone (mean 0.53 mg kg−1) and fumonisin (mean 0.49 mg kg−1). Levels of DON were more than fourfold higher and ZEA levels were 10‐fold higher in grain from hail‐damaged fields compared to undamaged fields. In approximately 50% of the grain samples from hail damaged fields, DON and zearalenone levels in ethanol co‐products would likely have been above FDA advisory levels and levels recommended by veterinarians, respectively. Preharvest scouting and screening of fields with suspected mycotoxins may be necessary, particularly with increased concerns about mycotoxin in grain end products.

High-resolution assessment of the hail hazard over complex terrain from radar and insurance data

A new method for the assessment of the hail hazard in high spatial resolution and its application for Southwest Germany are presented. By applying a cell tracking algorithm to 3D radar data, tracks of severe hailstorms are detected and merged with loss data from a building insurance company. Besides the detection of hailstorm tracks between 1997 and 2007, maximum reflectivity is projected on a 10 km x 10 km grid and analyzed by extreme value statistics. In doing so, radar reflectivities are related to statistical return periods. The results confirm a high spatial variability of both track density and hail hazard. Accordingly, severe hailstorms occur most frequently, and consequently also with highest intensities, in the region south of Stuttgart, whereas hail activity is lowest over the Rhine valley and the low mountain ranges of the Black Forest and Swabian Jura. Based on a conceptual approach, it is discussed how spatial differences in hail incidence can be explained plausibly by low Froude number flow (Fr < 1) around the mountains of Black Forest and the northwestern edge of the Swabian Jura, which causes downstream horizontal convergence.

A severe hailstorm over Guwahati airport and its vicinity on 2nd April 2006 : Synoptic and thermodynamic perspectives

Climatologically thunderstorm activity is quite common features over Guwahati Airport and its vicinity during premonsoon season. But a severe hailstorm with large size of hailstones and long duration is a rare event. Such a hailstorm with hailstone size of about 25mm occurred over Guwahati Airport (26.1°N, 91.6°E) on 2nd April, 2006 during midnight. In this paper an attempt has been made to investigate prerequisite synoptic and thermodynamic conditions of the atmosphere associated with this hailstorm. Under favourable synoptic and instability condition of thunderstorm occurrence, veering of winds over Guwahati between freezing level and 500 hPa level with vertical wind shear of horizontal winds exceeding 6.2 ms-1km-1 more appears to be conductive for the development of a hailstorm. Stability Indices viz., Showalter, K, Total-Total and Severe Weather Threat (SWEAT) index have shown predictability for this event.

A note on the severe hailstorm in North Cornwall on 16 October 2006

A note on the severe hailstorm in North Cornwall on 16 October 2006

Simulations of a hailstorm and the impact of CCN using an advanced two-moment cloud microphysical scheme

A hailstorm that caused significant damage in South-West Germany was simulated with the numerical weather prediction model COSMO. To cover hail evolution a sophisticated two-moment cloud microphysical scheme was extended by a particle class representing hail and implemented into COSMO. The horizontal resolution was 1 km. For initialization and boundary values COSMO forecasts with a coarser resolution and the standard one-moment microphysical scheme were used. Running this model system several convective cells develop including a severe hailstorm that resembles the observations qualitatively well and produces realistic amounts of precipitation and hail at the ground. Sensitivity studies were conducted varying the concentration of cloud condensation nuclei (CCN) and the shape of the cloud droplet size distribution (CDSD). Results show that both have a significant impact on hail accumulated at the ground and on the size of the hailstones. For two of the three CDSDs assumed the intensity of the severe storm decreases with increasing CCN concentration. However, this is not true for some of the weaker storms that form as well as for the third CDSD. Two model runs are analyzed and compared in more detail revealing the strong coupling between the numerous microphysical processes and between microphysics and dynamics. The sensitivity studies illustrate that the complexity of such storms makes it difficult to foresee, what will happen, when one microphysical parameter is changed. Thus, general conclusions whether an increase or decrease in CCN concentration invigorates a hailstorm cannot be drawn.

Study of the September 17th 2007 severe hailstorm in Pla d'Urgell. Part I: ground survey and hailpad analysis

Study of the September 17th 2007 severe hailstorm in Pla d'Urgell. Part I: ground survey and hailpad analysis