Forecast of high-impact weather over Italy: performance of global and limited-area ensemble prediction systems

Pincini, Giacomo (2018) Forecast of high-impact weather over Italy: performance of global and limited-area ensemble prediction systems. [Laurea magistrale], Università di Bologna, Corso di Studio in Fisica del sistema terra [LM-DM270]
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Abstract

The aim of this work is to assess the added value of the enhanced horizontal resolution in the probabilistic prediction of upper-level and surface fields. In particular, the performance of three different ensemble prediction systems were compared: ECMWF-ENS (51 members, 18 km horizontal resolution), COSMO-LEPS (16 members, 7 km horizontal resolution) and COSMO-2I-EPS (10 members, 2.2 km horizontal resolution). While the first 2 ensemble systems are operational, COSMO-2I-EPS is still in a development phase. Therefore, the intercomparison window covers a limited period, which ranges from 20 to 27 June 2016. In this work, both upper-level and surface variables are analyzed. As for upper-level, both temperature and the geopotential height at three different pressure levels are considered; the ensemble spread and the root mean square error are computed using the available Italian radiosounding data every 12/24 hours for verification. As for the surface, 2-metre temperature and precipitation cumulated over six hours are verified against the non-conventional station network provided by the National Civil Protection Department. The ensemble spread and the root mean square error of 2-metre temperature are computed, while a number of probabilistic scores (Brier Skill Score, Ranked Probability Score, Roc-Area, Outliers Percentage and others) are considered for precipitation. For both upper-level and surface verification, it turns out that the best scores are mainly obtained by the COSMO-based ensemble systems with higher horizontal resolution and lower ensemble size. The added value of high resolution in mesoscale ensemble systems seems to play a crucial role in the probabilistic prediction of atmospheric fields at all levels. In particular, the more detailed description of mesoscale and orographic-related processes in COSMO-ensembles provides an added value for the prediction of localised High-Impact Weather events.

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Pincini, Giacomo
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Ordinamento Cds
DM270
Parole chiave
Ensemble,Prediction,Systems,ECMWF ENS,COSMO-LEPS,COSMO-2I-EPS,High-Impact-Weather
Data di discussione della Tesi
19 Luglio 2018
URI

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