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Atlantic Jet: Stability of jet core

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Atlantic Jet: Stability of jet core – PowerPoint PPT presentation

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Title: Atlantic Jet: Stability of jet core


1
Atlantic JetStability of jet core
2
Thermal winds between 930 and 430 hpa
3
Look at cross sections where the baroclinicity
is greatest those positions are
4
Velocity in Cross section-Northern Hemisphere
5
Temperature in cross section-700hpa
6
Modern Stability
7
Modern Stability
8
LGM Stability
9
LGM Stability
10
Mid Atlantic Jet
  • Look at jet stability at location of greatest
    barotropic shear at 800 hpa

11
Mid Atlantic Jet
  • Also consider vorticity gradient

12
Find location of max shear and vorticity gradient
in LGM
Minnimum vorticity gradient Maximum Velocity Shear

13
Cross sections of zonal velocity at location of
maximum velocity shear
14
Mid atlantic modern stability- structure of eddy
15
Mid atlantic modern stability- Growth by layer
16
Mid atlantic LGM stability- Structure of Eddy
17
Mid atlantic LGM stability- Growth by layer
18
Seeding the mid-atlantic
  • Initialize the mid atlantic mean state jet with
    normal modes from the Western Atlantic
  • Look at growth rates instantaneously which can be
    determined by projection of tendency onto stream
    function or finite differencing of the standard
    deviation of perturbation time series (equivalent
    results)

19
Seeding the mid-atlantic
  • Modern normal mode growth rates are
  • Western Atlantic 3.7 10 -6
  • Mid Atlantic 2.6 10 -6

20
Seeding the mid-atlantic
  • LGM normal mode growth rates are
  • Western Atlantic 5.9 10 -6
  • Mid Atlantic 4.65 10 -6

21
2d Atlantic jet -LGM
  • Define a domain over which the thermal wind
    between 900 hPa and 400 hPa is above a threshold
    value.

LGM
22
2d Atlantic Jet - LGM
  • Transition between this 2d zonal velocity and the
    zonal mean zonal velocity, on a rectangular,
    singly periodic domain

23
2d Atlantic Jet - LGM
  • The jet has horizontal divergence which is nearly
    compensated for by vertical divergence
  • Match is not exact because the conversion from
    the sphere to the rectangle has a geometric
    factor--- IS THERE SOMETHING ELSE HERE?

LOWER LEVEL
24
2d Atlantic Jet- LGM
  • The jet has horizontal divergence which is nearly
    compensated for by vertical divergence
  • Match is not exact because the conversion from
    the sphere to the rectangle has a geometric
    factor--- IS THERE SOMETHING ELSE HERE?

UPPER LEVEL
25
2d Atlantic Jet - LGM
  • Find the meridional velocity which makes the jet
    non-divergent and has no flow through top and
    bottom boundary
  • -Doing both is impossible because there is
    vertical divergence and the conversion from the
    sphere to the rectangle has a geometric factor

LOWER LEVEL
26
2d Atlantic Jet - LGM
  • Find the meridional velocity which makes the jet
    non-divergent and has no flow through top and
    bottom boundary
  • -Doing both is impossible because there is
    vertical divergence and the conversion from the
    sphere to the rectangle has a geometric factor

UPPER LEVEL
27
2d Atlantic Jet - LGM
  • Eddies after 45 day integration

28
2d Atlantic Jet - LGM
  • Eddy growth in upper layer- growth rate 3.5
    10-6 Smaller than zonally invariant case
  • E fold in 3.3 days

29
2d Atlantic Jet - LGM
  • Size of eddies by region left half vs right
    half and middle half vs edge half

30
2d Atlantic Jet - LGM
  • Growth by region Projection of tendency onto
    streamfunction

31
2d Atlantic jet - MODERN
  • Define a domain over which the thermal wind
    between 900 hPa and 400 hPa is above a threshold
    value.

MODERN
MODERN
32
2d Atlantic Jet- MODERN
  • Transition between this 2d zonal velocity and the
    zonal mean zonal velocity, on a rectangular,
    singly periodic domain

33
2d Atlantic Jet- MODERN
  • The jet has horizontal divergence which is nearly
    compensated for by vertical divergence
  • Match is not exact because the conversion from
    the sphere to the rectangle has a geometric
    factor--- IS THERE SOMETHING ELSE HERE?

LOWER LEVEL
34
2d Atlantic Jet- MODERN
  • The jet has horizontal divergence which is nearly
    compensated for by vertical divergence
  • Match is not exact because the conversion from
    the sphere to the rectangle has a geometric
    factor--- IS THERE SOMETHING ELSE HERE?

UPPER LEVEL
35
2d Atlantic Jet - MODERN
  • Find the meridional velocity which makes the jet
    non-divergent and has no flow through top and
    bottom boundary
  • -Doing both is impossible because there is
    vertical divergence and the conversion from the
    sphere to the rectangle has a geometric factor

LOWER LEVEL
36
2d Atlantic Jet- MODERN
  • Find the meridional velocity which makes the jet
    non-divergent and has no flow through top and
    bottom boundary
  • -Doing both is impossible because there is
    vertical divergence and the conversion from the
    sphere to the rectangle has a geometric factor

UPPER LEVEL
37
2d Atlantic Jet-MODERN
  • Eddies after 25 day integration- vertical tilt
    53 degrees

38
2d Atlantic Jet - MODERN
  • Eddy growth in upper layer- growth rate 2.8
    10-6 Smaller than zonally invariant cases
  • E fold in 4 days-
  • _-Pulses between upper and lower level- NUMERICAL
    instability?

39
2d Atlantic Jet - MODERN
  • The eddy size and growth by region oscillates in
    time

Growth rate by region
Eddy size by region
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