gravity wave breaking beyond traditional instability concepts
Download
Skip this Video
Download Presentation
Gravity-wave breaking beyond traditional instability concepts

Loading in 2 Seconds...

play fullscreen
1 / 26

Gravity-wave breaking beyond traditional instability concepts - PowerPoint PPT Presentation


  • 71 Views
  • Uploaded on

Gravity-wave breaking beyond traditional instability concepts. U. Achatz Goethe-Universität Frankfurt am Main, Germany 6.10.2008. Gravity Waves in the Middle Atmosphere. Becker und Schmitz (2003). Gravity Waves in the Middle Atmosphere. Becker und Schmitz (2003).

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Gravity-wave breaking beyond traditional instability concepts' - xannon


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
gravity wave breaking beyond traditional instability concepts

Gravity-wave breaking beyond traditional instability concepts

U. Achatz

Goethe-Universität Frankfurt am Main, Germany6.10.2008

gw parameterizations
GW Parameterizations
  • multitude of parameterization approaches(Lindzen 1981, Medvedev und Klaassen 1995, Hines 1997, Alexander and Dunkerton 1999, Warner and McIntyre 2001)
  • too many free parameters
  • reasons :
    • insufficent knowledge: conditions of wave breaking
  • basic paradigm: breaking of a single wave
    • Stability analyses (NMs, SVs)
    • Direct numerical simulations (DNS)
basic types of gws
Basic Types of GWs

Dispersionsrelation:

Trägheitsschwerewellen (TSW):

Hochfrequente Schwerewellen (HSW):

basic types of gws1
Basic Types of GWs

Dispersion relation:

Trägheitsschwerewellen (TSW):

Hochfrequente Schwerewellen (HSW):

basic types of gws2
Basic Types of GWs

Dispersion relation :

Inertia-gravity waves (IGW):

Hochfrequente Schwerewellen (HSW):

basic types of gws3
Basic Types of GWs

Dispersion relation :

Inertia-gravity waves (IGW):

High-frequency gravity waves (HGW):

traditional instability concepts
Traditional Instability Concepts
  • static (convective) instability:
    • amplitude reference (a>1)
  • dynamic instability
  • limited applicability to HGW breaking
traditional instability concepts1
Traditional Instability Concepts
  • static (convective) instability:
    • amplitude reference (a>1)
  • dynamic instability
  • limited applicability to HGW breaking
traditional instability concepts2
Traditional Instability Concepts
  • static (convective) instability:
    • amplitude reference (a>1)
  • dynamic instability
  • BUT: limited applicability to GW breaking
gw instabilities beyond traditional concepts
GW Instabilities Beyond Traditional Concepts

IGW:

  • NM: Exponential energy growthsimple shear layer:
    • Static instability if
    • Dynamic instability if
  • SV: optimal energy growth over a finite time t(Farrell 1988a,b, Trefethen et al. 1993)

HGW:

  • Significant horizontal gradientsshear-layer concepts fail
gw instabilities beyond traditional concepts1
GW Instabilities Beyond Traditional Concepts

IGW:

  • NM: Exponential energy growthsimple shear layer:
    • Static instability if
    • Dynamic instability if
  • SV: optimal energy growth over a finite time t(Farrell 1988a,b, Trefethen et al. 1993)

HGW:

  • Significant horizontal gradientsshear-layer concepts fail(e.g. Lombard and Riley 1996, Achatz 2005)
breaking of an igw by an sv ri
Breaking of an IGW by an SV (Ri > ¼):

Measured dissipation rates 1…1000 mW/kg (Lübken 1997, Müllemann et al. 2003)

energetics
Energetics

not the gradients in z matter,but those in f!

instantaneous growth rate:

energetics1
Energetics

not the gradients in z matter,but those in f!

instantaneous growth rate:

energetics2
Energetics

not the gradients in z matter,but those in f!

instantaneous growth rate:

energetics of a breaking hgw with a 0 1
Energetics of a breaking HGW with a0 > 1

Strong growth perturbation energy:shear instability

energetics of a breaking hgw with a 0 11
Energetics of a Breaking HGW with a0 < 1

Strong growth perturbation energy:buoyancy instability

breaking hgw with a 0 1 dissipation rate
Breaking HGW with a0 < 1: Dissipation rate

Dissipation rate (mW/kg) at ist maximum (t = 5P):

summary
Summary
  • the Richardson number is not a good criterion for turbulence from gravity waves!
  • IGWs: Breaking by SVs
  • HGWs:Instabilities due to horizontal gradients
  • References:
    • Achatz (2005, Phys. Fluids)
    • Achatz and Schmitz (2006a,b, J.Atmos. Sci.)
    • Achatz (2007a,b, J. Atmos. Sci.)
    • Achatz (2007c, Adv. Space Res.)
    • all PDFs available from my web page (http://www.geo.uni-frankfurt.de/iau/ThMet/english/Publications/index.html)
  • see also Fritts et al. (2003, 2006, 2008a,b)
ad