Downscaling of ECMWF ensemble forecasts for cases of severe weather : Ensemble statistics and cluster analysis

Abstract Dynamical downscaling has been applied to global ensemble forecasts to assess its impact for four cases of severe weather (precipitation and wind) over various parts of Croatia. It was performed with the Croatian 12.2-km version of the Aire Limitee Adaptation Dynamique Developpement International (ALADIN) limited-area model, nested in the ECMWF TL255 (approximately 80 km) global ensemble prediction system (EPS). The 3-hourly EPS output was used to force the ALADIN model over the central European/northern Mediterranean domain. Results indicate that the identical clustering algorithm may yield differing results when applied to either global or to downscaled ensembles. It is argued that this is linked to the fact that a downscaled, higher-resolution ensemble resolves more explicitly small-scale features, in particular those strongly influenced by orographic forcing. This result has important implications in limited-area ensemble prediction, since it implies that downscaling may affect the interpreta...

[1]  E. Lorenz.  Atmospheric predictability experiments with a large numerical model , 1982 .

[2]  Prediction of the U.S. Storm of 24 26 January 2000 with the ECMWF Ensemble Prediction System , 2002 .

[3]  Thomas Jung,et al.  Reanalysis and reforecast of three major European storms of the twentieth century using the ECMWF forecasting system. Part II: Ensemble forecasts , 2005 .

[4]  Efi Foufoula-Georgiou,et al.  Scale issues in verification of precipitation forecasts , 2001 .

[5]  F. Molteni,et al.  The ECMWF Ensemble Prediction System: Methodology and validation , 1996 .

[6]  Roberto Buizza,et al.  The ECMWF Ensemble Prediction System , 1997 .

[7]  Eugenia Kalnay,et al.  Ensemble Forecasting at NMC: The Generation of Perturbations , 1993 .

[8]  S. Lakshmivarahan,et al.  8 . 3 VERIFICATION OF MESOSCALE FEATURES IN NWP MODELS , 2001 .

[9]  Performance of the ARPA-SMR limited-area ensemble prediction system: two flood cases , 2001 .

[10]  Roberto Buizza,et al.  A strategy for high‐resolution ensemble prediction. II: Limited‐area experiments in four Alpine flood events , 2001 .

[11]  Thomas Jung,et al.  Reanalysis and reforecast of three major European storms of the twentieth century using the ECMWF forecasting system. Part I: Analyses and deterministic forecasts , 2004 .

[12]  Michael R. Anderberg,et al.  Cluster Analysis for Applications , 1973 .

[13]  Harold E. Brooks,et al.  Using Ensembles for Short-Range Forecasting , 1999 .

[14]  E. Bazile,et al.  Implementation of a New Assimilation Scheme for Soil and Surface Variables in a Global NWP Model , 2000 .

[15]  Daniel S. Wilks,et al.  Statistical Methods in the Atmospheric Sciences: An Introduction , 1995 .

[16]  A. Hollingsworth,et al.  Storm prediction over Europe using the ECMWF Ensemble Prediction System , 2002 .

[17]  R. Buizza.  Potential Forecast Skill of Ensemble Prediction and Spread and Skill Distributions of the ECMWF Ensemble Prediction System , 1997 .

[18]  G. Shutts.  Dynamical aspects of the October storm, 1987: a study of a successful fine-mesh simulation , 1990 .

[19]  T. Palmer,et al.  Stochastic representation of model uncertainties in the ECMWF ensemble prediction system , 2007 .

[20]  F. Atger,et al.  Tubing: An Alternative to Clustering for the Classification of Ensemble Forecasts , 1999 .

[21]  Inger-Lise Frogner,et al.  High‐resolution limited‐area ensemble predictions based on low‐resolution targeted singular vectors , 2002 .

[22]  F. Molteni,et al.  A strategy for high‐resolution ensemble prediction. I: Definition of representative members and global‐model experiments , 2001 .

[23]  B. Ivancan-Picek,et al.  Effects of different initial and boundary conditions in ALADIN/HR simulations during MAP IOPs , 2006 .

[24]  Martina Tudor,et al.  Use of high-resolution dynamical adaptation in operational suite and research impact studies , 2004 .

[25]  Giulia Panegrossi,et al.  The 9 10 November 2001 Algerian Flood: A Numerical Study. , 2005 .

[26]  William H. Press,et al.  The Art of Scientific Computing Second Edition , 1998 .

[27]  P. L. Houtekamer,et al.  A System Simulation Approach to Ensemble Prediction , 1996 .

[28]  Roberto Buizza,et al.  The Soverato flood in Southern Italy: performance of global and limited-area ensemble forecasts , 2003 .

[29]  F. A. Seiler,et al.  Numerical Recipes in C: The Art of Scientific Computing , 1989 .