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John E. Janowiak, Peter Bauer, Wanqiu Wang, Phillip A. Arkin, and Jon Gottschalck

predictions have been conducted over the past few decades. Janowiak (1992) evaluated the performance of short-range forecasts (12–36 h) of precipitation that were generated by the operational numerical weather prediction models (ca. 1989) at the European Centre for Medium-Range Weather Forecasts (ECMWF) and at the National Centers for Environmental Prediction (NCEP) in the United States. One of the conclusions in that paper was that while the models did a very good job of representing the seasonal and

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Thomas M. Hamill, Jeffrey S. Whitaker, Michael Fiorino, and Stanley G. Benjamin

convection scheme type, mixing-length formulation, and turbulent vertical diffusion parameter. (More details on these are provided online at .) d. European Centre for Medium-Range Weather Forecasts The ECMWF EPS used the ECMWF Integrated Forecast System (IFS) model, versions 35r2 (prior to 8 September 2009) and 35r3 (after 8 September 2009). Model resolution was T399L62 for both versions, or about 45-km grid spacing at

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E. A. Irvine, S. L. Gray, J. Methven, and I. A. Renfrew

targeted observation coverage and number using a two-dimensional sampling pattern. Targeted observations were spaced according to the horizontal correlation length scales assumed by the European Centre for Medium-Range Weather Forecasts (ECMWF) four-dimensional variational data assimilation (4D-Var) scheme, and the number of observations and size of target region were varied. Taking targeted observations over a larger area was found to be more effective. The proximity of the targeted observations to

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Mio Matsueda, Masayuki Kyouda, Zoltan Toth, H. L. Tanaka, and Tadashi Tsuyuki

), the European Centre for Medium-Range Weather Forecasts (ECMWF), the Japan Meteorological Agency (JMA), the Korea Meteorological Administration (KMA), Météo-France, the National Centers for Environmental Prediction (NCEP), and the Met Office (UKMO)] were producing daily global ensemble forecasts (1–2 weeks ahead), delivering in near–real time a selection of forecast data to the TIGGE portals at CMA, ECMWF, and the National Center for Atmospheric Research (NCAR). More than 3 years have passed since

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Warren J. Tennant, Glenn J. Shutts, Alberto Arribas, and Simon A. Thompson

improvements to the atmospheric observing system, increased computing power, and more sophisticated models, the development of operational EPS suites took place at, inter alia, the National Centers for Environmental Prediction (NCEP; Toth and Kalnay 1993 ), the Meteorological Service of Canada (MSC; Houtekamer et al. 1996 ), and the European Centre for Medium-Range Weather Forecasts (ECMWF; Buizza and Palmer 1995 ; Molteni et al. 1996 ). Some centers focused on estimating uncertainty in initial

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Ronald Gelaro, Rolf H. Langland, Simon Pellerin, and Ricardo Todling

and Space Administration (NASA) Global Modeling and Assimilation Office (GMAO), Environment Canada (EC), the European Centre for Medium-Range Weather Forecasts (ECMWF), and Météo France. This paper presents results from three forecast systems: the Navy Operational Global Atmospheric Prediction System (NOGAPS) of NRL, the Goddard Earth Observing System-5 (GEOS-5) of GMAO, and the Global Deterministic Prediction System (GDPS) of EC. It is anticipated that follow-on experiments will include

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Benoît Vié, Olivier Nuissier, and Véronique Ducrocq

sampling the probability density function for the initial state with different techniques. Global EPSs were first implemented at the European Centre for Medium-Range Weather Forecasts (ECMWF) using the computation of singular vectors ( Molteni et al. 1996 ), and at the National Centers for Environmental Prediction (NCEP) through the breeding modes technique. The Meteorological Service of Canada used an ensemble data assimilation technique and, more recently, an ensemble Kalman filter to generate the

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Sharanya J. Majumdar, Kathryn J. Sellwood, Daniel Hodyss, Zoltan Toth, and Yucheng Song

data released over the northeastern Pacific Ocean on medium-range forecasts downstream. Using a 51-member European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble ( Buizza et al. 2003 ), they concluded that the ETKF is capable of discriminating between observation locations that are effective and ineffective for 3–6-day National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) forecasts of 200-hPa winds within a verification region based on Rossby wave dispersion

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William A. Komaromi, Sharanya J. Majumdar, and Eric D. Rappin

Prediction System (NOGAPS), and the European Centre for Medium-Range Forecasts (ECMWF) model revealed that the ECMWF produced the most realistic vortex initialization. Therefore, twice-daily 1° × 1° horizontal resolution ECMWF analyses are used to provide initial and boundary conditions for the WRF domain in this study. For each TC case, a “control” (nonperturbed) simulation, and an array of “perturbed” simulations in which the initial conditions are modified by local, balanced perturbations of vorticity

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Elizabeth Satterfield and Istvan Szunyogh

reflect the local observation density: the uncertainty is underestimated in regions of high observation density, such as Europe, Japan, and the United States, and overestimated in regions of lower observational density, such as the Southern Hemisphere and the oceanic regions. This result is an indication that our zonally constant covariance inflation factor cannot be tuned to be optimal everywhere when there are zonal changes in observation density. Thus, we conjecture that implementing a spatially

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