Scale-dependent verification of ensemble forecasts

TitleScale-dependent verification of ensemble forecasts
Publication TypeMiscellaneous
Year of Publication2008
AuthorsJung, T, Leutbecher, M
Secondary TitleTechnical Memorandum
Date PublishedJanuary
Type of WorkTechnical Memorandum

A scale-dependent verification of the ECMWF ensemble prediction system (EPS) in the Northern Hemisphere is presented. The relationship between spread and skill is investigated alongside probabilistic forecast skill for planetary, synoptic and sub-synoptic spectral bands. The filtering is accomplished using total and zonal wavenumber filters. Diagnosed overdispersiveness of ECMWF EPS in the short-range is primarily due to excessive amount of spread on synoptic scales. Diagnosed underdispersiveness of the ensemble beyond day 5 of the forecast, can be explained by too little spread on both synoptic and planetary scales.