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| Titel |
Analysis of heavy rainstorms in the Mediterranean climate area |
| VerfasserIn |
Oreste Terranova, Stefano Luigi Gariano |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080871
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| Zusammenfassung |
| In recent decades, violence and frequency of torrential rain events are increased in the
Mediterranean basin context, despite the decrease of the annual rainfall, because of climate
change. In particular, in Italy both annual precipitation and the number of wet days show a
decrease, while the precipitation intensity increases. When severe rainfall events hit small
basins, the damage of flash floods is notable also due to the high content of solid material
from soil slips and mud/debris flows that take place on the slopes. The direct measurement of
the parameters for the physical processes of interest are rarely available, then, special
attention must be given to the study of spatial and temporal variability of rainfall at the
sub-hourly scale. The availability of a large number of observations with high temporal
detail has made it possible analysing the spatial and temporal variability of heavy
rainstorms occurred in the last two decades in Calabria that, because of its climatic
peculiarities can be considered as representative of many areas of the Mediterranean
basin.
The present study aims to improve, from a statistical point of view, the understanding, at
sub-hourly scale, of the structure temporal and spatial of short duration (< 24 h) and intense
rainfall events that have hit Calabria (southern Italy), causing flash floods. For this purpose, a
rainfall event was classified as heavy rainstorm if its amount, PEV , is greater than a given
threshold (i.e. 100 mm d-1). The spatial analysis regards the heavy rainstorms that
have hit, totalizing more than 50 mm d-1 at each other rain gauge present in an
area > 500 km2. In this way, the heavy rainstorms are classified as extended or
localized.
To describe the structure of the storms, the use of standardized rainfall profiles, SRP, to
compare them, by simplifying analyses and presentation of data, is adopted in this study.
Besides, a new criterion is adopted to identify the shape of the profiles, based on the
comparison between the areas A1, A2, A3, A4 – related to the quartiles of the SRP – and the
corresponding four values of the uniform SRP.
In order to analyze the spatial and temporal characteristics of heavy rainstorms, a further
selection is conducted, to identify those having the greatest potential to produce a strong
social impact and increase the perception of risk associated with the interaction between
nature and society. In this regard, it is assumed that the following constraints were met:
PEV >100 mm; I30 >50 mm h-1; EJ >30 J. In the case study, 902 events were
detected characterized by PEV >100 mm, 604 by I30 >50 mm h-1, 369 by EJ -¥30
J.
The location – classified according to elevation, distance to the coast, homogeneous
sub-regions, etc. – of the rain gauges with the highest number of events characterized by high
values of PEV , I30 and EJ allowed to identify the sectors of the territory more
frequently affected by heavy rainstorms and their spatial and temporal structure. |
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