Advances in Geosciences
www.adv-geosci.net
1680-7340
1680-7359
16
Observation, Prediction and Verification of Precipitation (EGU Session 2007)
2008
10.5194/adgeo-16-89-2008
http://www.adv-geosci.net/16/89/2008/
http://www.adv-geosci.net/16/89/2008/adgeo-16-89-2008.html
http://www.adv-geosci.net/16/89/2008/adgeo-16-89-2008.pdf
89
95
2008-04-09
A LEPS approach to the predictability of intense rain storms in the Central Mediterranean basin
S. Federico
s.federico@isac.cnr.it
C. Bellecci
R. L. Walko
CNR-ISAC, Strada prov.le Lecce-Monteroni km 1.2, 73100, Lecce, Italy
CRATI Scrl, c/o Università della Calabria, Rende (CS), Italy
Facoltà di Ingegneria-Università di "Tor Vergata", via del Politecnico 1, Rome , Italy
Pratt School, Duke University, Durham, NC, USA
This study investigates a method for best member selection of a Limited area
model Ensemble Prediction System (LEPS) with the goal to increase
quantitative precipitation forecast. A case study that occurred between
22-24 May 2002 over Calabria, southern Italy, is discussed.
<br><br>
Mediterranean storms often develop under upper level disturbances which are
usually associated with high values of potential vorticity. Anomalously high
values of potential vorticity can be identified by the METEOSAT water vapor
channel centered around 6.3 μm because they are associated with dark
band on the METEOSAT image. This signature offers a chance to identify the
upper level disturbance that can be exploited in data void countries as
Calabria.
<br><br>
The working hypothesis is that the uncertainty in the representation of the
upper-level disturbance has a major impact on the precipitation forecast.
This issue is utilized in an ensemble forecast where member forecasts are
compatible with the analysis and forecast errors. These members are grouped
in five clusters by a hierarchical clustering technique which utilizes the
height of the dynamical tropopause to compute distances between members.
Therefore the members of a cluster have a similar representation of the
upper level disturbance. For each cluster a representative member is
selected and its pseudo water vapor image is compared with the corresponding
METEOSAT 7 water vapor image at a specific time, antecedent to the rain
occurrence over Calabria. The subjective evaluation of the comparison allows
to gain physical insight in the storm evolution and to select representative
members which are more in agreement with the METEOSAT image.
<br><br>
Results, even if for a case study, show the feasibility of the methodology
that, if confirmed by further investigations, could be valuable in data void
countries as the central Mediterranean basin.
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