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Benedikt Schulz and Sebastian Lerch

. To quantify forecast uncertainty, most operationally used NWP models generate probabilistic predictions in the form of ensembles of deterministic forecasts that differ in initial conditions, boundary conditions, or model specifications. Despite substantial improvements over the past decades ( Bauer et al. 2015 ), ensemble forecasts continue to exhibit systematic errors that require statistical postprocessing to achieve accurate and reliable probabilistic forecasts. Statistical postprocessing has

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Mirjam Hirt, Stephan Rasp, Ulrich Blahak, and George C. Craig

ground to 22 km above mean sea level. Shallow convection is parameterized using the Tiedtke scheme. Details on parameterizations can be found in Doms et al. (2011) . The setup follows the operational COSMO-DE setup with 461 by 421 grid points centered over Germany at 50°N, 10°E. The only major deviation from the current operational setup is a change of the tuning parameter tur_len in the boundary layer scheme to 500 m. As discussed in the introduction, a smaller value was applied as an ad hoc

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Kevin Bachmann, Christian Keil, George C. Craig, Martin Weissmann, and Christian A. Welzbacher

, Fig. 2 ) encompassing 461 × 421 grid points with a horizontal grid spacing of 0.025° or 2.8 km. The vertical coordinates are identical to the idealized setup, and the same parameterizations as in the idealized setup are applied. We use an asymptotic vertical mixing length of the boundary layer turbulence scheme of 500 m, as in the idealized configuration, but in contrast to the current operational value of 150 m. This facilitates not only direct comparisons to the idealized setup, but also removes

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Stephan Rasp, Tobias Selz, and George C. Craig

1. Introduction Diabatic processes in the atmosphere, especially the release of latent heat through condensation and freezing, have been shown to have a large impact on atmospheric dynamics by modifying the upper-tropospheric potential vorticity (PV) distribution. Warm conveyor belts (WCB) are the predominant diabatically influenced phenomena in the midlatitudes. They are defined as broad airstreams that originate from the boundary layer of the cyclone’s warm sector and subsequently rise along

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Marlene Baumgart, Paolo Ghinassi, Volkmar Wirth, Tobias Selz, George C. Craig, and Michael Riemer

convection-permitting simulations on very large, preferably global, domains and for long lead times. Such an approach is computationally extremely costly, but has recently been performed for a single case by Judt (2018) . This approach, however, is currently not feasible to be applied to a large number of cases with several ensemble members to ensure the robustness of the results. Using coarser resolution with a deterministic scheme to parameterize convection, upscale error growth turns out to be much

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Christian Euler, Michael Riemer, Tobias Kremer, and Elmar Schömer

counterintuitive to see air masses from the boundary layer at the initial positions when looking at downward motions of air parcels in the inner core. The fact that air parcels from the same region are part of the inner-core convection ( Figs. 6d,f,h ) indicates that air parcels in the inner core of Karl perform a rollercoaster-like movement while circulating upward inside the core. Since the seeding of the trajectories in the inner core is a snap-shot of the current state at seeding time, some of those air

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

across the boundary of the integration domain [second term in Eq. (5) ]. Not explicitly included in the barotropic framework of Boer (1984) , the third term in Eq. (5) constitutes an error source due to the divergence of the quasi-horizontal (adiabatic) flow. The remaining terms describe the influence of nonconservative processes (term 4), the boundary contribution due to changes in the integration area (term 5), and the residual (term 6). We evaluate the PV error tendency equation on an

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Hilke S. Lentink, Christian M. Grams, Michael Riemer, and Sarah C. Jones

) and http://www.cosmo-model.org for more details on the computational methods]. The model is set up with a horizontal resolution of 0.025° (about 2.5 km at 35°N) and 57 vertical levels up to 30-km height, with an enhanced vertical resolution in the planetary boundary layer. Shallow convection is parameterized using the mass-flux scheme of Tiedtke (1989) , while middle and high convection are explicitly computed. For all parameterized processes, the default setup of COSMO is used ( Doms et al

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Michael Maier-Gerber, Michael Riemer, Andreas H. Fink, Peter Knippertz, Enrico Di Muzio, and Ron McTaggart-Cowan

the analysis and forecast hours and are functions of the matrix indices and , respectively. This formulation ensures that the warp path aligns the tracks in a monotonic and continuous manner. In addition to these implicit conditions, another rule is imposed for the boundaries. For forecast tracks that last longer than the first 48 h after the formation of the pre-Chris cyclone in the analysis, the later part is not considered in the calculation of . The warping path starts with the

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Paolo Ghinassi, Georgios Fragkoulidis, and Volkmar Wirth

Mcintyre 1976 ), N represents nonconservative processes, and the symbol indicates a term that scales with the third power of wave amplitude α . In addition, wave activity plays an important role in the so-called nonacceleration theorem ( Charney and Drazin 1961 ), which can be written as where represents the zonally averaged zonal wind. For linear and conservative waves the above two equations have two important implications: first, wave activity is globally conserved (given suitable boundary

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