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| Titel |
Climatology of damage-causing hailstorms over Germany |
| VerfasserIn |
M. Kunz, M. Puskeiler, M. Schmidberger |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060128
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| Zusammenfassung |
| In several regions of Central Europe, such as southern Germany, Austria, Switzerland, and
northern Italy, hailstorms often cause substantial damage to buildings, crops, or automobiles
on the order of several million EUR. In the federal state of Baden-Württemberg, for
example, most of the insured damage to buildings is caused by large hailstones.
Due to both their local-scale extent and insufficient direct monitoring systems, hail
swaths are not captured accurately and uniquely by a single observation system.
Remote-sensing systems such as radars are able to detect convection signals in a basic
way, but they lack the ability to discern a clear relation between measured intensity
and hail on the ground. These shortcomings hamper statistical analysis on the hail
probability and intensity. Hail modelling thus is a big challenge for the insurance
industry.
Within the project HARIS-CC (Hail Risk and Climate Change), different meteorological
observations are combined (3D / 2D radar, lightning, satellite and radiosounding data) to
obtain a comprehensive picture of the hail climatology over Germany. The various
approaches were tested and calibrated with loss data from different insurance companies
between 2005 and 2011. Best results are obtained by considering the vertical distance
between the 0°C level of the atmosphere and the echo top height estimated from 3D
reflectivity data from the radar network of German Weather Service (DWD). Additionally,
frequency, intensity, width, and length of hail swaths are determined by applying a cell
tracking algorithm to the 3D radar data (TRACE3D; Handwerker, 2002). The hailstorm
tracks identified are merged with loss data using a geographical information system (GIS) to
verify damage-causing hail on the ground.
Evaluating the hailstorm climatology revealed that hail probability exhibits high spatial
variability even over short distances. An important issue is the spatial pattern of hail
occurrence that is considered to be due to orographic modifications of the flow. It is found
that hail probability downstream of the low mountain ranges of Germany is strongly
controlled by the Froude number. In the case of low Froude number flow, a convergence zone
may develop downstream of the mountains, which may lead to the triggering or
intensification of deep convection.
Based on the results obtained, a hail loss model will be created for the insurance marked
to convert the observed hail parameter into monetary parameters, for example, mean loss or
maximum loss. Such a model will allow to quantify the hail risk for a certain return period on
the local-scale or to assess worst case scenarios. |
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