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| Titel |
Intensity-Duration-Frequency (IDF) rainfall curves, for data series and climate projection in African cities |
| VerfasserIn |
Francesco De Paola, Maurizio Giugni, Maria Elena Topa, Adrien Coly, Kumelachew Yeshitela, Wilbard Kombe, Emmanuel Tonye, Hamidou Touré |
| 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 |
250073584
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| Zusammenfassung |
| The intensity-duration-frequency curves are used in hydrology to express in a synthetic way,
the link between the maximum rainfall height h and a generic duration d of a rainfall event,
fixed a given return period T.
Generally, IDF curves can be characterized by a bi-parameter power law:
h(d,T) = a(T)dn
where a(T), and n are the parameters that have to be estimated through a probabilistic
approach.
An intensity-duration-frequency analysis starts by gathering time series record of
different durations and extracting annual extremes for each duration. The annual extreme data
are then fitted by a probability distribution.
The present study, carried out within the FP7-ENV-2010 CLUVA project (CLimate
change and Urban Vulnerability in Africa), regards the evaluation of the IDF curves for five
case studies: Addis Ababa (Ethiopia), Dar Es Salaam (Tanzania), Douala (Cameroon),
Ouagadouogou (Burkina Faso) and Saint Louis (Senegal).
The probability distribution chosen to fit the annual extreme data is the classic Gumbel
distribution.
However, for the case studies, only the maximum annual daily rainfall heights are
available. Therefore, to define the IDF curves and the extreme values in a smaller time
window (10’, 30’, 1h, 3h, 6h, 12h), it is required to develop disaggregation techniques of the
collected data, in order to generate a synthetic sequence of rainfall, with statistical properties
equal to the recorded data.
The daily rainfalls were disaggregated using two models:
short-time intensity disaggregation model (10’, 30’, 1h);
cascade-based disaggregation model (3h, 6h, 12h).
On the basis of disaggegation models and Gumbel distribution , the parameters of the IDF curves
for the five test cities were evaluated.
In order to estimate the contingent influence of climate change on the IDF curves, the
illustrated procedure has been applied to the climate (rainfall) simulations over the
time period 2010-2050 provided by the CMCC (Centro Euro-Mediterraneo sui
Cambiamenti Climatici). The climate projections used were performed following the IPCC
(Intergovernmental Panel on Climate Change) 20C3M protocol for the 20th Century, using
the RCP4.5 and RCP8.5 radiative forcing scenarios and are characterized by vertical
resolutions of 8 and 1 km.
In conclusion, the evaluation of the IDF curves allowed to frame the rainfall evolution of
the five case studies, first considering only historical data, then taking in account the climate
projections, in order to verify the changes in rainfall patterns. In particular, taking in account
the climate projections, an increase of rainfall frequency can be highlighted, compared to a
decrease of intensity. |
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