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Paolo Ghinassi
,
Georgios Fragkoulidis
, and
Volkmar Wirth

1. Introduction An important feature of midlatitude atmospheric dynamics is the existence of upper-tropospheric Rossby waves with synoptic- to planetary-scale wavenumbers. Often a Rossby wave is not strictly circumglobal; rather, its amplitude is spatially inhomogeneous with a relative maximum at a specific location decaying to smaller values at larger distances. This gives rise to so-called Rossby wave packets [RWPs; for a recent review see Wirth et al. (2018) ]. A key feature of RWPs is the

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
Benedikt Schulz
and
Sebastian Lerch

of the stationwise (left) mean bias of the ensemble median and (right) mean ensemble range of the EPS as functions of the lead time. The black line indicates the average over all samples. The temporal development of the bias and ensemble range shown in Fig. 4 indicates another meteorological effect, the evening transition of the planetary boundary layer. When the sun sets, the surface and low-level air that have been heated over the course of the day cool down and thermally driven

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

phase. Beyond this synoptic-scale phase saturation at long lead times (beyond 2 weeks), the results of Buizza and Leutbecher (2015) indicate that there is still forecast skill for large-scale fields. To investigate error growth up to the planetary scale, we employ a complementary diagnostic that filters out phase information and identifies the envelope of the upper-level Rossby waves. This diagnostic is based on finite-amplitude local wave activity (LWA) in the primitive-equation, isentropic

Open access
Georgios Fragkoulidis
and
Volkmar Wirth

1. Introduction Rossby waves are a dominant feature of the midlatitude upper-tropospheric circulation at synoptic to planetary scales ( Rossby 1940 ; Haurwitz 1940 ). Owing their existence to the rotation and the spherical shape of Earth, they take the form of large-scale meanders in the westerly winds ( Rhines 2015 ). On the weather time scale, Rossby wave activity typically varies in longitude and time and tends to organize in the so-called Rossby wave packets (RWPs), rather than

Open access
Andreas Schlueter
,
Andreas H. Fink
,
Peter Knippertz
, and
Peter Vogel

( Matsuno 1966 ). Two other major wave types have been observed in the tropical belt that are not obtained from the shallow-water equations: the Madden–Julian oscillation (MJO; Madden and Julian 1971 ) and westward traveling tropical disturbances (TDs) including easterly waves ( Riehl 1945 ). All these waves are collectively termed “tropical waves” in this paper. The spatiotemporal scales range from planetary and 30–90 days in the case of the MJO to synoptic and 1–3 days in the case of inertio

Open access
Rachel H. White
,
Kai Kornhuber
,
Olivia Martius
, and
Volkmar Wirth

. 2019 ), as well as extreme precipitation and/or flooding ( Blackburn et al. 2008 ; Schubert et al. 2011 ; Hirata and Grimm 2016 ; de Vries 2021 ). Rossby waves manifest as meridional undulations in the extratropical atmospheric circulation, resulting from the conservation of a dynamical property known as potential vorticity (PV); PV is a function of both relative and planetary vorticity, and of static stability. Owing to the rotation and the sphericity of Earth, planetary vorticity increases

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

wavenumber, which measures the number of full wavelengths as one goes around the globe. Planetary-scale Rossby waves are typically characterized by zonal wavenumbers , whereas synoptic-scale Rossby waves are characterized by higher wavenumbers. Another idealized incarnation of a Rossby wave would be a single trough or ridge being equivalent to a single dipole of υ . However, except in very rare cases, a Rossby wave appears neither as a purely sinusoidal circumglobal wave nor as a single trough or ridge

Open access
George C. Craig
,
Andreas H. Fink
,
Corinna Hoose
,
Tijana Janjić
,
Peter Knippertz
,
Audine Laurian
,
Sebastian Lerch
,
Bernhard Mayer
,
Annette Miltenberger
,
Robert Redl
,
Michael Riemer
,
Kirsten I. Tempest
, and
Volkmar Wirth

Waves to Weather (W2W) is a collaborative research center formed to investigate the limits of predictability of weather. Our ability to make forecasts up to a week or more in advance contributes to a strong economy and protects human life and property. Although we commonly speak of “weather,” particularly high-impact weather events take many different forms that result from different physical processes. The most destructive weather disasters in recent years have been associated with floods and

Open access