 |
| Titel |
Application of the LEPS technique for Quantitative Precipitation Forecasting (QPF) in Southern Italy: a preliminary study |
| VerfasserIn |
S. Federico, E. Avolio, C. Bellecci, M. Colacino, R. L. Walko |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1023-5809
|
| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 13, no. 1 ; Nr. 13, no. 1 (2006-03-24), S.53-66 |
| Datensatznummer |
250011704
|
| Publikation (Nr.) |
 copernicus.org/npg-13-53-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
This paper reports preliminary results for a Limited area model Ensemble
Prediction System (LEPS), based on RAMS (Regional Atmospheric Modelling
System), for eight case studies of moderate-intense precipitation over
Calabria, the southernmost tip of the Italian peninsula. LEPS aims to
transfer the benefits of a probabilistic forecast from global to regional
scales in countries where local orographic forcing is a key factor to force
convection.
To accomplish this task and to limit computational time in an operational
implementation of LEPS, we perform a cluster analysis of ECMWF-EPS runs.
Starting from the 51 members that form the ECMWF-EPS we generate five
clusters. For each cluster a representative member is selected and used to
provide initial and dynamic boundary conditions to RAMS, whose integrations
generate LEPS. RAMS runs have 12-km horizontal resolution.
To analyze the impact of enhanced horizontal resolution on quantitative
precipitation forecasts, LEPS forecasts are compared to a full Brute Force
(BF) ensemble. This ensemble is based on RAMS, has 36 km horizontal
resolution and is generated by 51 members, nested in each ECMWF-EPS member.
LEPS and BF results are compared subjectively and by objective scores.
Subjective analysis is based on precipitation and probability maps of case
studies whereas objective analysis is made by deterministic and
probabilistic scores. Scores and maps are calculated by comparing ensemble
precipitation forecasts against reports from the Calabria regional raingauge
network.
Results show that LEPS provided better rainfall predictions than BF for all
case studies selected. This strongly suggests the importance of the enhanced
horizontal resolution, compared to ensemble population, for Calabria for
these cases.
To further explore the impact of local physiographic features on QPF
(Quantitative Precipitation Forecasting), LEPS results are also compared
with a 6-km horizontal resolution deterministic forecast. Due to local and
mesoscale forcing, the high resolution forecast (Hi-Res) has better
performance compared to the ensemble mean for rainfall thresholds larger
than 10mm but it tends to overestimate precipitation for lower amounts.
This yields larger false alarms that have a detrimental effect on objective
scores for lower thresholds.
To exploit the advantages of a probabilistic forecast compared to a
deterministic one, the relation between the ECMWF-EPS 700 hPa geopotential
height spread and LEPS performance is analyzed. Results are promising even
if additional studies are required. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|