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| Titel |
An ensemble study of HyMeX IOP6 and IOP7a: sensitivity to physical and initial and boundary condition uncertainties |
| VerfasserIn |
A. Hally, E. Richard, V. Ducrocq |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Sciences ; 14, no. 5 ; Nr. 14, no. 5 (2014-05-09), S.1071-1084 |
| Datensatznummer |
250118434
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| Publikation (Nr.) |
 copernicus.org/nhess-14-1071-2014.pdf |
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| Zusammenfassung |
| The first Special Observation Period of the HyMeX campaign took place
in the Mediterranean between September and November 2012 with the
aim of better understanding the mechanisms which lead to heavy
precipitation events (HPEs) in the region during the autumn
months. Two such events, referred to as Intensive Observation Period 6
(IOP6) and Intensive Observation Period 7a (IOP7a), occurred
respectively on 24 and 26 September over south-eastern
France. IOP6 was characterised by moderate to weak low-level flow
which led to heavy and concentrated convective rainfall over the
plains near the coast, while IOP7a had strong low-level flow and
consisted of a convective line over the mountainous regions further
north and a band of stratiform rainfall further east. Firstly, an
ensemble was constructed for each IOP using analyses from the AROME,
AROME-WMED, ARPEGE and ECMWF operational models as initial (IC) and
boundary (BC) conditions for the research model Meso-NH at
a resolution of 2.5 km. A high level of model skill was seen
for IOP7a, with a lower level of agreement with the observations for
IOP6. Using the most accurate member of this ensemble as a CTRL
simulation, three further ensembles were constructed in order to
study uncertainties related to cloud physics and surface turbulence
parameterisations. Perturbations were introduced by perturbing the
time tendencies of the warm and cold microphysical and turbulence
processes. An ensemble where all three sources of uncertainty were
perturbed gave the greatest degree of dispersion in the surface
rainfall for both IOPs. Comparing the level of dispersion to that of
the ICBC ensemble demonstrated that when model skill is low (high)
and low-level flow is weak to moderate (strong), the level of
dispersion of the ICBC and physical perturbation ensembles is (is
not) comparable. The level of sensitivity to these perturbations is
thus concluded to be case dependent. |
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