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Christian M. Grams and Heather M. Archambault

location of recurvature following Archambault et al. (2015) . That is, the fields are shifted for each case so that recurvature occurs at the mean recurvature location (25.5°N, 133.3°E). Temporarily, the fields are composited at 6-hourly time steps starting 3 days prior to recurvature ( T − 72 h) to 7 days after recurvature ( T + 168 h). b. Composite fields as initial and boundary conditions The recurvature-relative composite fields are used as initial and boundary conditions for numerical

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Kirstin Kober and George C. Craig

2006 ). Multiple integrations of NWP models (ensembles) can be used to provide probabilistic information but can be set up in different ways, depending on the represented sources of uncertainty. Recent studies have shown that in different weather regimes, different sources of uncertainty dominate: in cases of strong large-scale forcing, initial and boundary conditions uncertainty contributes more to the overall uncertainty, whereas in weak large-scale forcing, model error is more important

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Tobias Selz and George C. Craig

-Range Weather Forecasts (ECMWF) to provide the initial and boundary conditions whereas DWD uses their own global model. As at DWD the interpolation from the global model was not done directly, but a 7-km version of COSMO was used as intermediate step. Note that COSMO uses a rotated spherical grid, which in our setup is centered at 50°N, 10°E. We focus on the period 19–23 July 2007 in which an almost stationary low pressure system over Great Britain caused several days with intense convective activity and a

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Kirstin Kober, Annette M. Foerster, and George C. Craig

1. Introduction The skill of numerical forecasts of convective precipitation is limited by several sources of uncertainty that can be minimized, but never completely removed. The initial and the boundary conditions for the model integration have limited accuracy and additionally physical processes have to be approximated and truncated to the model’s grid. Furthermore, the atmosphere is chaotic and the physical nature of convection stochastic. Ensembles of different model integrations and their

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Franziska Teubler and Michael Riemer

inversion domain extends from 20° to 80°N, with vertical boundary conditions specified at 875 and 125 hPa. Zonally, the domain is approximately centered on the RWP and usually spans the hemisphere. As discussed in section 2 , upper-level PV advection by the wind field v qb associated with upper-level PV anomalies themselves is referred to as quasi-barotropic dynamics in this study. The upper-level PV advection by the wind field v bc associated with low-level PV anomalies is referred to as

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Andreas Schäfler, Andreas Dörnbrack, Christoph Kiemle, Stephan Rahm, and Martin Wirth

2008 ; Miglietta and Rotunno 2009 ), or low-level moisture supply ( Boutle et al. 2010 ; Keil et al. 2008 ), and their physical representation in NWP models has emerged to play a crucial role for QPF. In particular, the supply of low-level moisture by latent heat fluxes or through advective transport is crucial for the evolution of midlatitude weather systems. As pointed out by Boutle et al. (2010) , large-scale moisture advection is the process that maintains the structure of the boundary layer

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Andrea Schneidereit, Silke Schubert, Pavel Vargin, Frank Lunkeit, Xiuhua Zhu, Dieter H. W. Peters, and Klaus Fraedrich

train. As this wave train is apparent throughout the troposphere ( Orsolini and Nikulin 2006 ), the large-scale flow seems to play an important role in European heat waves. Model simulations indicate that the anomalous circulation during the summer of 2010 over eastern Europe can be ascribed primarily to natural internal atmospheric variability rather than to climate change or ocean boundary conditions like sea surface temperature or sea ice extent ( Dole et al. 2011 ), reflecting changes in the

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Martin Weissmann, Florian Harnisch, Chun-Chieh Wu, Po-Hsiung Lin, Yoichiro Ohta, Koji Yamashita, Yeon-Hee Kim, Eun-Hee Jeon, Tetsuo Nakazawa, and Sim Aberson

operational Korea Meteorological Administration (KMA) Global Data Assimilation and Prediction System (GDAPS) forecast data (0000 and 1200 UTC) from 1 to 30 September 2008. The WRF model was used for forecasts up to a lead time of 72 h. The horizontal resolution was 30 km (190 × 190 grid points) and the GDAPS (T426L40) global model data were used for initial and boundary conditions. The physics packages included the WSM6 microphysics scheme, the Kain–Fritsch cumulus parameterization scheme, the Noah land

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Marlene Baumgart, Michael Riemer, Volkmar Wirth, Franziska Teubler, and Simon T. K. Lang

PV inversion (PPVI) under nonlinear balance ( Charney 1955 ; Davis 1992 ). The PPVI is performed on the Northern Hemisphere between 25° and 85°N on 15 evenly spaced pressure levels, with vertical boundary conditions specified at 875 and 125 hPa. Anomalies are defined as deviations from a background state, which is here defined as the 30-day mean (centered at 0000 UTC 14 November 2013) of the analysis. We use a midtropospheric pressure level (600 hPa) as the separation level between upper- and

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Maxi Boettcher and Heini Wernli

very few DRWs approach the downstream continent during their propagation phase (cf. section 2 ). This indicates that either the conditions for DRW propagation are not favorable in the eastern part of the ocean basins (due to reduced baroclinicity and/or boundary layer humidity) or that DRWs are overtaken by an upper-level disturbance before reaching the eastern oceans. Fig . 6. Track density of DRW centers in the years 2001–10 from genesis till decay (number of events within 3° × 3° boxes) in the

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