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Franziska Teubler and Michael Riemer

). While the diagnostic presented in the current study will not be formally related to wave-activity conservation laws, we hope that such a link can be established in future work. Eddy kinetic energy (EKE) and individual contributions to its tendency provide a well-established framework with which to analyze the evolution of RWPs (e.g., Orlanski and Sheldon 1995 ; Chang 2000 ; Chang et al. 2002 ). Within that framework, the paradigm of downstream baroclinic development has been established. Starting

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Tobias Selz and George C. Craig

perturbation amplitudes and structures may, however, originate from the boundary layer in an environment with high convective available potential energy (CAPE) and convective inhibition. Here perturbations might be able to trigger additional convective cells instead of just displacing existing ones ( Leoncini et al. 2010 ). Furthermore there is evidence that the upscale impact of convection on the geostrophically balanced flow may also depend strongly on the convective regime (i.e., if the convective

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

water vapor and the associated latent heat release are thought to be a major weakness in the formulation of current operational NWP models. The diagnosis of “forecast–analysis” differences of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) by Didone (2006) and Dirren et al. (2003) revealed characteristic patterns of forecast errors on the downstream side of the cold front of the extratropical cyclones. Among the observational errors of the initial

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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

interpolation ( Wu et al. 2002 ): the background field (the previous 6-h forecast) is combined with observations with a 3D-Var multivariate formalism ( Kleist et al. 2009 ). Dropsonde observations within a radius of 111 km from the typhoon center (or 3 times the specified radius of maximum wind if larger than 111 km) are currently not used in the NCEP analysis ( Aberson 2008 ). c. KMA WRF experiment description One experiment with dropsondes (DROP) and a control run without additional observations (NODROP

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Michael Riemer, Marlene Baumgart, and Sven Eiermann

the recurving tropical cyclone (e.g., Riemer and Jones 2010 , section 5.2.2). It is therefore plausible to hypothesize that jet streaks downstream of ET play a particularly prominent role for cyclogenesis. The purpose of the current study is to test this hypothesis. To quantify the contributions of the upper-level trough and the jet streak to downstream cyclogenesis, the vertical motion attributable to these features will be analyzed. Section 2 recalls the relationship between vertical motion

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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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Lars Wiegand, Arwen Twitchett, Cornelia Schwierz, and Peter Knippertz

stress or friction velocity by its first-order control low-level wind speed U , we can define the PDU in the following way: where U t denotes the constant threshold velocity that is typically on the order of 8 m s −1 at 10 m above the ground ( Chomette et al. 1999 ). As 10-m winds are not a prognostic variable in TIGGE models, it has to be computed through extrapolation from the lowest model level using parameters from the boundary layer scheme. The details of this procedure can lead to dramatic

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Christian M. Grams and Heather M. Archambault

1. Introduction The large-scale midlatitude flow is dominated by the upper-level jet stream that serves as a waveguide for Rossby waves (e.g., Martius et al. 2010 ). Because their general evolution follows dry dynamics that can be represented at grid scale in numerical weather prediction (NWP) models, Rossby waves may be expected to feature a high degree of predictability ( Grazzini and Vitart 2015 ). However, major forecast uncertainty and error in the midlatitudes in current NWP models have

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Gabriel Wolf and Volkmar Wirth

packet and smoothly decays to smaller values at the boundaries of the wave packet. The carrier wave C oscillates between positive and negative values and varies on a much shorter spatial scale than A . The amplitude A will also be referred to as envelope in the following. The task of envelope reconstruction is tantamount as to find an algorithm that allows one to compute A ( λ ) when υ ( λ ) is given. In the past, meteorologists have used essentially two methods in order to reach this goal

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