ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna

Bologna, Italy

ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna

Bologna, Italy
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Ceppi A.,Polytechnic of Milan | Ravazzani G.,Polytechnic of Milan | Salandin A.,A.R.P.A. Piemonte | Rabuffetti D.,A.R.P.A. Piemonte | And 3 more authors.
Natural Hazards and Earth System Science | Year: 2013

In recent years the interest in the forecast and prevention of natural hazards related to hydro-meteorological events has increased the challenge for numerical weather modelling, in particular for limited area models, to improve the quantitative precipitation forecasts (QPF) for hydrological purposes.

After the encouraging results obtained in the MAP D-PHASE Project, we decided to devote further analyses to show recent improvements in the operational use of hydro-meteorological chains, and above all to better investigate the key role played by temperature during snowy precipitation.

In this study we present a reanalysis simulation of one meteorological event, which occurred in November 2008 in the Piedmont Region. The attention is focused on the key role of air temperature, which is a crucial feature in determining the partitioning of precipitation in solid and liquid phase, influencing the quantitative discharge forecast (QDF) into the Alpine region. This is linked to the basin ipsographic curve and therefore by the total contributing area related to the snow line of the event.

In order to assess hydrological predictions affected by meteorological forcing, a sensitivity analysis of the model output was carried out to evaluate different simulation scenarios, considering the forecast effects which can radically modify the discharge forecast.

Results show how in real-time systems hydrological forecasters have to consider also the temperature uncertainty in forecasts in order to better understand the snow dynamics and its effect on runoff during a meteorological warning with a crucial snow line over the basin.

The hydrological ensemble forecasts are based on the 16 members of the meteorological ensemble system COSMO-LEPS (developed by ARPA-SIMC) based on the non-hydrostatic model COSMO, while the hydrological model used to generate the runoff simulations is the rainfall-runoff distributed FEST-WB model, developed at Politecnico di Milano. © 2013 Author(s).

Montani A.,ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna | Cesari D.,ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna | Marsigli C.,ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna | Paccagnella T.,ARPA SIMC HydroMeteoClimate Regional Service of Emilia Romagna
Tellus, Series A: Dynamic Meteorology and Oceanography | Year: 2011

In this work, the main characteristics of COSMO-LEPS, the Limited-area Ensemble Prediction System developed in the framework of the COnsortium for Small-scale MOdelling, are presented. The present status of the system is shown with the description of the methodology and of the main upgrades which took place during its years of activity. The performance of COSMO-LEPS for the probabilistic prediction of precipitation is assessed in terms of both time-series and seasonal scores over a 7-yr period. A fixed number of stations are selected and observations are compared to short and early medium-range forecasts. Different verification indices are used to assess the skill of COSMO-LEPS and to identify the impact of system modifications on forecast skill. The different system upgrades are found to impact positively on COSMO-LEPS performance, with a gain of 2d of predictability in the last 4 yr of operational forecasts. This holds when the skill of the system is assessed both for single events (e.g. precipitation surpassing a fixed threshold) and for multi-event situations. Scores for fixed forecast ranges but varying thresholds confirm increasingly better performance of the system. For a few seasons, the performance of COSMO-LEPS is also assessed in terms of probabilistic prediction of some upper-air variables. Then, the skill of COSMO-LEPS is compared to that of the global-ensemble system providing the boundaries, to identify the extent to which skill improvements may relate to those of the driving ensemble. Finally, the main streams of development for COSMO-LEPS system are discussed with future possible upgrades and methodology modifications. © 2011 The Authors Tellus A © 2011 John Wiley & Sons A/S.

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