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Julia H. Keller, Christian M. Grams, Michael Riemer, Heather M. Archambault, Lance Bosart, James D. Doyle, Jenni L. Evans, Thomas J. Galarneau Jr., Kyle Griffin, Patrick A. Harr, Naoko Kitabatake, Ron McTaggart-Cowan, Florian Pantillon, Julian F. Quinting, Carolyn A. Reynolds, Elizabeth A. Ritchie, Ryan D. Torn, and Fuqing Zhang

contributing to baroclinic conversion. The upper-tropospheric divergent outflow contributes to the ageostrophic geopotential flux. In an isentropic PV framework, (generalized) vertical motion is represented by diabatic heating, and hence diabatic PV modification is directly diagnosed. The upper-tropospheric divergent outflow is diagnosed as a separate process. More details on the differences between the two frameworks are provided by Teubler and Riemer (2016) and Wirth et al. (2018) . Interpreting PV

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Jacopo Riboldi, Christian M. Grams, Michael Riemer, and Heather M. Archambault

atmospheric blocking . Geophys. Res. Lett. , 31 , L06125 , . 10.1029/2003GL019341 Small , D. , E. Atallah , and J. R. Gyakum , 2014 : An objectively determined blocking index and its Northern Hemisphere climatology . J. Climate , 27 , 2948 – 2970 , . 10.1175/JCLI-D-13-00374.1 Stoelinga , M. T. , 1996 : A potential vorticity-based study of the role of diabatic heating and friction in a numerically simulated

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Stephan Rasp, Tobias Selz, and George C. Craig

PV in the presence of diabatic heating can be approximated with the following equation ( Eliassen and Kleinschmidt 1957 ): where is the vertical component of the absolute vorticity, θ is the potential temperature, and ρ is the air density. Upper-level PV modification through diabatic heating can, therefore, occur by the modification of PV through (1) and by the vertical, cross-isentropic advection of PV from the lower troposphere, where the climatological PV values are much lower due to

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Andreas Schäfler, George Craig, Heini Wernli, Philippe Arbogast, James D. Doyle, Ron McTaggart-Cowan, John Methven, Gwendal Rivière, Felix Ament, Maxi Boettcher, Martina Bramberger, Quitterie Cazenave, Richard Cotton, Susanne Crewell, Julien Delanoë, Andreas Dörnbrack, André Ehrlich, Florian Ewald, Andreas Fix, Christian M. Grams, Suzanne L. Gray, Hans Grob, Silke Groß, Martin Hagen, Ben Harvey, Lutz Hirsch, Marek Jacob, Tobias Kölling, Heike Konow, Christian Lemmerz, Oliver Lux, Linus Magnusson, Bernhard Mayer, Mario Mech, Richard Moore, Jacques Pelon, Julian Quinting, Stephan Rahm, Markus Rapp, Marc Rautenhaus, Oliver Reitebuch, Carolyn A. Reynolds, Harald Sodemann, Thomas Spengler, Geraint Vaughan, Manfred Wendisch, Martin Wirth, Benjamin Witschas, Kevin Wolf, and Tobias Zinner

troposphere ( Wernli and Davies 1997 ), which influences the structure and evolution of midlatitude surface cyclones (e.g., Kuo et al. 1991 ; Davis et al. 1993 ; Binder et al. 2016 ). Above the level of maximum latent heating, PV is reduced by cloud diabatic processes, leading to negative PV anomalies in the upper-tropospheric WCB outflow region ( Wernli 1997 ; Pomroy and Thorpe 2000 ; Madonna et al. 2014 ; Methven 2015 ). The divergent outflow winds (region 3 in Fig. 1 ) tend to amplify the upper

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

error tendency equation. Our tendency equation is based on the local tendency equation for PV in isentropic coordinates, which is given by (e.g., Davies and Didone 2013 ) where describes the nonconservative PV tendency due to diabatic heating and nonconservative momentum change as measured by the parameterization schemes. The heating rate comprises heating due to the cloud, convection, radiation, and turbulence parameterization, while the horizontal wind tendency components of ( and

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Volkmar Wirth, Michael Riemer, Edmund K. M. Chang, and Olivia Martius

the perturbation under mean-flow deformation and shear. A comparable deformation term is missing from the Ertel-PV framework of Teubler and Riemer (2016) because the PV tendency is spatially averaged and the PV anomalies are not inverted to yield the associated wind and geopotential height anomalies. Another difference is in the treatment of diabatic processes. Diabatic heating does not directly enter the EKE equation, but instead appears indirectly through an enhancement of baroclinic

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

Coriolis parameter, and is the isentropic layer density with gravitational acceleration g and pressure p . The PV tendency is given by advection and nonconservative PV modification, where describes the nonconservative PV modification due to diabatic heating and nonconservative momentum change. The heating rates and horizontal wind tendencies are approximated by centered differences of accumulated tendencies 1 from the parameterization schemes (convection, microphysics, long- and shortwave

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Toward a Systematic Evaluation of Warm Conveyor Belts in Numerical Weather Prediction and Climate Models. Part I: Predictor Selection and Logistic Regression Model

Julian F. Quinting and Christian M. Grams

moisture supply in the warm sector (e.g., Field and Wood 2007 ; Boutle et al. 2011 ; Schäfler and Harnisch 2015 ; Berman and Torn 2019 ; Dacre et al. 2019 ). Overall, the latent heating increases the potential temperature of the air parcels on average by 20 K ( Eckhardt et al. 2004 ; Madonna et al. 2014b ). Below and close to the level of maximum latent heating, a cyclonic potential vorticity (PV) anomaly is produced, which may affect the subsequent life cycle of the associated midlatitude low

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Tobias Selz, Lotte Bierdel, and George C. Craig

variability of the KE spectrum on small scales in summer months suggests a relationship between the amount of small-scale KE and cumulus convection. To investigate this hypothesis, we correlate the KE at each wavenumber with the precipitation rate. Since the dataset does not distinguish between convective and stratiform precipitation, we use the total precipitation rate, and since the dynamical response to convective heating is spread over a broad range of scales ( Bierdel et al. 2017 , 2018 ), we use

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Andreas Schlueter, Andreas H. Fink, and Peter Knippertz

. 2009 ). Moisture anomalies starting at low levels, rise to midlevels prior to the convective peak. A stratiform moist outflow is left behind after the passage of the deep convection. In addition to adiabatic heating associated with the vertical circulation, diabatic effects create heating that slows down the wave. The reader is referred to Kiladis et al. (2009) for a more detailed review of the theory, observational evidence, and properties of CCEWs. Two additional disturbances dominate rainfall

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