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Christopher Polster
and
Volkmar Wirth

dynamics, but it can accommodate the impact of diabatic processes in the form of LWA sources and sinks. Global influence of planetary waves can be incorporated at least one-way as preconditioning of the waveguide or the background-level wave activity. Paradise et al. (2019) used the idealized NH18 numerical model of the zonal LWA budget to investigate the response of blocking prevalence, frequency, and persistence to changes in the transient forcing of eddies, the stationary wave amplitude, and

Open access
Volkmar Wirth
and
Christopher Polster

.0.CO;2 . 10.1175/1520-0469(1981)038<1179:TSLROA>2.0.CO;2 Hoskins , B. J. , and T. Ambrizzi , 1993 : Rossby wave propagation on a realistic longitudinally varying flow . J. Atmos. Sci. , 50 , 1661 – 1671 , https://doi.org/10.1175/1520-0469(1993)050<1661:RWPOAR>2.0.CO;2 . 10.1175/1520-0469(1993)050<1661:RWPOAR>2.0.CO;2 Huntingford , C. , D. Mitchell , K. Kornhuber , D. Coumou , S. Osprey , and M. Allen , 2018 : Assessing changes in risk of amplified planetary waves in a

Open access
Paolo Ghinassi
,
Marlene Baumgart
,
Franziska Teubler
,
Michael Riemer
, and
Volkmar Wirth

1. Introduction The upper-tropospheric flow in the midlatitudes is characterized by the presence of planetary-scale waves, called Rossby waves ( Rossby 1940 ; Rhines 2002 ). Rossby waves are important for understanding the atmospheric general circulation because they are able to transport energy and momentum across large distances ( Charney and Drazin 1961 ; Hoskins and Karoly 1981 ). On the synoptic scale (i.e., zonal wavenumbers 6–8), Rossby waves often materialize in the form of Rossby

Open access
Tobias Selz

background spectrum and thus likely involve a climatological component. For example, orography and the land–sea distribution may hinder the largest planetary waves from freely evolving. In addition the ICON simulations have fixed sea surface temperatures. d. Comparison to simulations with a deterministic convection scheme A second set of simulations has been performed using the ICON model but this time in its standard setup with the deterministic TB convection scheme ( Bechtold et al. 2001 ). With this

Open access
Tobias Selz
,
Michael Riemer
, and
George C. Craig

average. To identify when and how the intrinsic limit might impact the skill of future forecasting systems, it is necessary to understand the transition in error growth processes as initial condition accuracy improves. Sun and Zhang (2016) investigated predictability by means of idealized baroclinic wave experiments with a variety of initial condition perturbations. They found that for small-amplitude initial condition perturbations, rapid error growth on convective scales is triggered, which is

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

smoothed with a Gaussian filter. Next we focus on week 3, the time when WCB outflow frequency biases saturate ( Fig. 9 ). Similar results are found for weeks 2 and 4 (not shown). First we investigate if a link of WCB outflow biases and biases in the upper-tropospheric large-scale flow, as depicted by geopotential height at 300 hPa, exist. Generally the forecasted large-scale extratropical flow in winter is too zonal and the planetary wave pattern is slightly shifted in week 3 ( Fig. 9b ): over the

Open access
Julian F. Quinting
and
Christian M. Grams

. 2020 ). Thus, an adequate representation of WCBs is desirable in NWP and climate models. First introduced by Browning et al. (1973) and Harrold (1973) , WCBs are defined as cyclone-relative airstreams that ascend from the planetary boundary layer to the upper troposphere along vertically sloping isentropic surfaces. Assuming the absence of nonconservative forces, early studies identified WCBs using cyclone-relative streamlines on a wet-bulb potential temperature surface (e.g., Harrold 1973

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Christian Barthlott
and
Corinna Hoose

profiles then lead to differences in the stability and relative humidity, both of which are highly relevant to cloud formation and precipitation. The advantage of this method is that the dominating weather regime and the environmental conditions in the planetary boundary layer and at cloud base are not changed. To cover different weather regimes, this technique is applied to days with weak synoptic forcing (airmass convection) and strong synoptic forcing (passage of frontal zones). In each of these

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