Search Results

You are looking at 1 - 10 of 20 items for :

  • Multi-Scale Dynamics of Gravity Waves (MS-GWaves) x
  • Refine by Access: All Content x
Clear All
Andreas Dörnbrack

. East of 30°E, the low-level winds became more southerly. The polar-front jet at 300 hPa had developed above a region of enhanced middle- and lower-tropospheric baroclinicity, the polar front as seen in Fig. 1b . This upper-level jet streak had a large along-stream extent and was nearly zonally oriented at 45°N and V H > 70 m s −1 in its core ( Fig. 2b ). During the considered period, the polar-front jet bent and advanced southward in conjunction with the deepening upper-level trough. Similar to

Open access
Fabienne Schmid, Elena Gagarina, Rupert Klein, and Ulrich Achatz

-resolution numerical weather simulations in large domains. An example is the spontaneous emission of IGWs by jets and fronts, the latter arising in the development of synoptic-scale midlatitude dynamics. Various numerical studies have considered idealized dynamical systems to investigate this emission mechanism for IGWs and to gain an improved understanding of the underlying physical processes (e.g., O’Sullivan and Dunkerton 1995 ; Zhang 2004 ; Wang and Zhang 2007 ; Plougonven and Snyder 2007 ; Hien et al

Restricted access
Christopher G. Kruse, M. Joan Alexander, Lars Hoffmann, Annelize van Niekerk, Inna Polichtchouk, Julio T. Bacmeister, Laura Holt, Riwal Plougonven, Petr Šácha, Corwin Wright, Kaoru Sato, Ryosuke Shibuya, Sonja Gisinger, Manfred Ern, Catrin I. Meyer, and Olaf Stein

stratospheric polar night jet (PNJ) is significant (e.g., Sato et al. 2012 ; Jiang et al. 2013 ; Hendricks et al. 2014 ; Amemiya and Sato 2016 ; Wright et al. 2017 ; Jiang et al. 2019 ). In a broader context, this region is of interest as many climate models exhibit the so-called cold-pole problem (e.g., Eyring et al. 2010 ), where lower-stratospheric polar temperatures are too cold in the Southern Hemisphere winter and spring, the meridional temperature gradient is too strong, and (via thermal wind

Restricted access
Victor C. Mayta and Ángel F. Adames

component is significant at the 95% level or greater. The location of the T3 ARM site (3.2°S, 60.6°W) is indicated by a green star. On the other hand, the maximum divergence at 850 hPa is located in the east of the region of maximum convection. Similar low-level features of 2-day waves are documented in Tulich and Kiladis (2012) . Convection, as observed in Fig. 3b , promotes strong easterlies resulting in low-level jet occurrences along with the wave passage ( Fig. 3a ). This mechanism affects the

Open access
Tyler Mixa, Andreas Dörnbrack, and Markus Rapp

times. Gravity waves with short horizontal wavelengths are generally not included in global circulation models due to their high resolution requirements and their limited influence according to linear gravity wave theory. Linear theory for stationary mountain waves predicts a cutoff wavelength of λ x cutoff = 2 πu / N ≳ 30–50 km inside the polar night jet (PNJ) ( Schoeberl 1985 ). This cutoff suggests a widespread existence of turning levels for mountain waves with λ x ≲ 30 km in the winter

Open access
Sonja Gisinger, Andreas Dörnbrack, Vivien Matthias, James D. Doyle, Stephen D. Eckermann, Benedikt Ehard, Lars Hoffmann, Bernd Kaifler, Christopher G. Kruse, and Markus Rapp

tropospheric jet streams generate vertically propagating gravity waves in the troposphere and lower stratosphere ( Smith 1979 ; Gill 1982 ; Baines 1995 ; Fritts and Alexander 2003 ; Nappo 2012 ; Sutherland 2010 ; Plougonven and Zhang 2014 ). Through their far-field interactions, gravity waves constitute an important coupling mechanism in Earth’s atmosphere. The associated redistribution of momentum and energy controls the global middle-atmospheric circulation ( Dunkerton 1978 ; Lindzen 1981 ). To

Full access
Mozhgan Amiramjadi, Ali R. Mohebalhojeh, Mohammad Mirzaei, Christoph Zülicke, and Riwal Plougonven

are orography, convection, and coupled jet and front systems (e.g., Plougonven and Zhang 2014 ), which are mainly located in the troposphere. Based on their sources, the IGWs are thus classified into “orographic” and “nonorographic” (e.g., Kim et al. 2003 ) and dealt with separately in IGW parameterization schemes as they have distinct characteristics and impacts ( McLandress et al. 2013 ). Through their sources, the nonorographic IGWs are connected to the large-scale flow which is dominantly

Full access
David C. Fritts, Ronald B. Smith, Michael J. Taylor, James D. Doyle, Stephen D. Eckermann, Andreas Dörnbrack, Markus Rapp, Bifford P. Williams, P.-Dominique Pautet, Katrina Bossert, Neal R. Criddle, Carolyn A. Reynolds, P. Alex Reinecke, Michael Uddstrom, Michael J. Revell, Richard Turner, Bernd Kaifler, Johannes S. Wagner, Tyler Mixa, Christopher G. Kruse, Alison D. Nugent, Campbell D. Watson, Sonja Gisinger, Steven M. Smith, Ruth S. Lieberman, Brian Laughman, James J. Moore, William O. Brown, Julie A. Haggerty, Alison Rockwell, Gregory J. Stossmeister, Steven F. Williams, Gonzalo Hernandez, Damian J. Murphy, Andrew R. Klekociuk, Iain M. Reid, and Jun Ma

= flight level, SI = South Island, CW = convective waves, FWs = frontal waves, SO = Southern Ocean. IOPs are shown in the context of the large-scale ECMWF horizontal winds from 0 to 80 km in Fig. 4 (top). The dominant feature is the polar night jet with a maximum wind often exceeding 100 m s −1 at ∼50–60 km that is presumably modulated in strength by PWs on time scales of ∼5–10 days. The poleward jet associated with frontal systems exhibits episodic maxima of ∼30–50 m s −1 at ∼8–12 km on similar

Full access
Andreas Dörnbrack, Stephen D. Eckermann, Bifford P. Williams, and Julie Haggerty

scientific objectives of this survey flight into the atmospheric flow above the Southern Ocean were based on operational forecasts by a suite of high resolution numerical weather prediction (NWP) models ( Fritts et al. 2016 , their Table 3) and were formulated as follows prior to the actual flight: to sample a region near Macquarie Island where forecasts suggested strong gravity wave generation and deep propagation from an exit and splitting region of the tropospheric midlatitude jet, here, called the

Open access
Mahnoosh Haghighatnasab, Mohammad Mirzaei, Ali R. Mohebalhojeh, Christoph Zülicke, and Riwal Plougonven

Alexander 2003 ) over long distances and interacting with other phenomena through, for example, triggering convection. Previous observational and numerical studies have shown several sources for IGWs as orography, convection, shear instability, jet streams, and fronts (e.g., Uccellini and Koch 1987 ; Eckermann and Vincent 1993 ; O’Sullivan and Dunkerton 1995 ; Guest et al. 2000 ; Plougonven and Snyder 2007 ). The IGWs affect the atmospheric general circulation through breaking and dissipation by

Free access