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Volkmar Wirth and Christopher Polster

recovers the underlying reference state and is not fraught by artifacts arising from the presence of the eddies. To be sure, the concept of the zonalized background state makes only sense in the idealized framework of conservative dynamics. By contrast, the evolution of growing eddies in the real atmosphere may be affected by nonconservative processes to some extent ( Pfahl et al. 2015 ). We, therefore, need to assume that these nonconservative effects are of minor importance. However, this does not

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Jan Wandel, Julian F. Quinting, and Christian M. Grams

vorticity (PV)–potential temperature ( θ ) framework ( Hoskins et al. 1985 ) in order to describe the two major effects of the latent heat release on the further evolution of the WCB and its impact on midlatitude dynamics. First, latent heat release contributes to the formation of a cyclonic PV anomaly below the level of maximum heating. This diabatically generated PV anomaly contributes to the formation of the extratropical cyclone’s PV tower ( Rossa et al. 2000 ) and thus to its overall intensity

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Eva-Maria Walz, Marlon Maranan, Roderick van der Linden, Andreas H. Fink, and Peter Knippertz

reason for this is the exceptionally high degree of convective organization observed over tropical Africa ( Nesbitt et al. 2006 ; Roca et al. 2014 ), a process that is difficult to capture with the convective parameterizations used in global NWP models ( Vogel et al. 2018 ). Kniffka et al. (2020) confirm the overall low skill in predicting local rainfall in Africa but show a positive effect of propagating synoptic-scale disturbances on forecasts of regional precipitation. The overall poor

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Joël Arnault, Thomas Rummler, Florian Baur, Sebastian Lerch, Sven Wagner, Benjamin Fersch, Zhenyu Zhang, Noah Kerandi, Christian Keil, and Harald Kunstmann

respective effects can finally be assessed by comparison to S ENS . f. Weather regime dependence In regional atmospheric modeling, internal processes uncertainty preferentially affects precipitation during weak synoptic forcing episodes (e.g., Stensrud et al. 2000 ; Keil et al. 2014 ). The question here is, if the precipitation sensitivity to the uncertainty in the representation of terrestrial water flow also depends on the level of synoptic forcing. Keil et al. (2014) used the convective adjustment

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Christian Barthlott and Corinna Hoose

( Rosenfeld et al. 2008 ). The larger water load at the freezing level results in an additional release of latent heat, leading to an invigoration of convection with additional rainfall. Even in absence of such a thermodynamic invigoration, Fan et al. (2013) found that aerosol’s microphysical effects can lead to a dramatic increase in cloud cover, cloud-top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the

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Peter Vogel, Peter Knippertz, Andreas H. Fink, Andreas Schlueter, and Tilmann Gneiting

horizon to few days at scales of 100 km ( Judt 2020 ). Third, small-scale physical processes such as cloud microphysics and radiation can relatively easily affect scales large enough to be of interest to predictions through their effects on the vertical profiles of latent (and radiative) heating and thus divergent wind. For example, convective invigoration by increased cloud condensation nuclei ( Rosenfeld et al. 2008 ) and larger or longer-lived anvils ( Fan et al. 2013 ) affect convective

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

convection to determine if the anticipated physical effects are present. Based on these results, a revised version of the PSP scheme will be defined that has the potential to improve forecast skill for convective precipitation. To demonstrate improved skill will require a systematic evaluation of ensemble forecasts over a long test period. This will be the subject of a future study. The PSP scheme ( Kober and Craig 2016 ) aims to better couple subgrid turbulence to convective initiation by reintroducing

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Roderick van der Linden, Andreas H. Fink, Joaquim G. Pinto, and Tan Phan-Van

from the Integrated Global Radiosonde Archive (IGRA; Durre et al. 2006 ). Table 1. Geographical information on the five stations in Quang Ninh Province (cf. Fig. 1 ) from which hourly rainfall measurements are available. Five-digit station ID numbers indicate a surface synoptic observation (SYNOP) station and three-digit station IDs are regional station IDs. Fig . 2. Box-and-whisker plots of accumulated rainfall (mm) during 1200 UTC 25 Jul–1200 UTC 3 Aug. The availability of historical data is

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

the forecast errors associated with these changes. For mature TCs that make landfall, on the other hand, many (idealized) studies document the influence of either a flat coastal region or an orographic barrier (e.g., Taiwan) on the track and structural development. When a TC vortex impinges on land, regardless of orography, it has two effects: a reduction of moisture supply and an increase of surface roughness. First, when the inner core is still over the ocean, dry air from land is transported

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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

Atlantic THORPEX Regional Campaign (ATReC; Rabier et al. 2008 ), Winter Storm Reconnaissance (WSR, e.g., Szunyogh et al. 2000 ), the THORPEX Pacific Asian Regional Campaign (T-PARC, Weissmann et al. 2011 ), and the Convective and Orographically Induced Precipitation Study/European THORPEX Regional Campaign (COPS/ETReC 2007; Wulfmeyer et al. 2011 ), which all focused on the impact of additional observations on improving forecast accuracy. This idea was pioneered by the Fronts and Atlantic Storm

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