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| Titel |
Trend analysis of convective indices relevant for hail events in Germany |
| VerfasserIn |
Susanna Mohr, Michael Kunz |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250051743
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| Zusammenfassung |
| Severe thunderstorms and associated extreme events such as hail represent a substantial
hazard potential for buildings, crops, and critical infrastructure. In the last decades, damage
caused by severe hailstorms has significantly increased in Central Europe. In the southwest of
Germany, more than 40% of all damage to buildings by natural hazards is associated with
large hail (1986-2008). In the light of global warming, the questions arise if the thunderstorm
potential of the atmosphere already has changed and which changes will be expected in the
future.
The purpose of this work is to investigate the probability of occurrence and the intensity of
thunderstorm events by means of trend analysis of different atmospheric parameters that give
information about atmospheric stability. At seven sounding stations in Germany
(complemented by additional Central European stations) appropriate convective indices were
statistically analyzed. By comparing hail loss data from a building insurance company with
several convective indices, those parameters with the highest prediction skill for hail were
identified. The evaluation with synoptic station data confirmed the temporal homogeneity of
the sounding data. Accordingly, changes in the instrumentation of the sondes are not relevant
for the trends.
First results show that the convective potential in atmosphere has changed significantly in the
last decades. For a time period of 32 years (1978-2009), convective parameters
considering near-surface values of temperature and moisture display mainly a trend
towards higher convective potential (like CAPEsurface, LIsurface). On the other hand,
most of the parameters computed from temperature and dew point at higher levels
or mixed over the lowest 100 hPa show a decrease in the thunderstorm potential
(Showalter-Index, CAPE100hPa, LI100hPa). The different trend directions can be
explained by different trends in temperature and dew point at the various layers.
While the temperature at all examined layers in the 12UTC soundings has been
increased, the dew point at all stations show an increase only near the surface. At
higher levels, only two stations revealed a significant increase in the dew point
temperature.
By varying the time series (1957 until 2009) with respect to their start and end date, the
stability of the linear trends and their significance was tested. It was found that most of the
convective indices show a trend to more intense convection during the last two decades,
whereas the change in the trend direction happens later in the north of Germany (mid-1990s)
compared to the south (beginning 1990s).
Within the frame of in the project „Haris-CC“ (Hail risk and changing climate) it is planned
to describe past hailstorms by a multi-dimensional parameter space of appropriate
meteorological indicators (e.g., convective energy, moisture flux convergence, large-scale
weather patterns), obtained from reanalysis-data and soundings. The methods will be
transferred to an ensemble of high resolution regional climate model simulations. Future
changes of the hail hazard will be projected from the current hazard and the climate change
signal. |
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