Atlantic Jet: Stability of jet core

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Atlantic JetStability of jet core
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Thermal winds between 930 and 430 hpa
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Look at cross sections where the baroclinicity
is greatest those positions are
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Velocity in Cross section-Northern Hemisphere
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Temperature in cross section-700hpa
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Modern Stability
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Modern Stability
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LGM Stability
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LGM Stability
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Mid Atlantic Jet

• Look at jet stability at location of greatest
  barotropic shear at 800 hpa

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Mid Atlantic Jet

• Also consider vorticity gradient

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

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Cross sections of zonal velocity at location of
maximum velocity shear
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Mid atlantic modern stability- structure of eddy
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Mid atlantic modern stability- Growth by layer
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Mid atlantic LGM stability- Structure of Eddy
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Mid atlantic LGM stability- Growth by layer
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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)

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Seeding the mid-atlantic

• Modern normal mode growth rates are
• Western Atlantic 3.7 10 -6
• Mid Atlantic 2.6 10 -6

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Seeding the mid-atlantic

• LGM normal mode growth rates are
• Western Atlantic 5.9 10 -6
• Mid Atlantic 4.65 10 -6

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2d Atlantic jet -LGM

• Define a domain over which the thermal wind
  between 900 hPa and 400 hPa is above a threshold
  value.

LGM
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2d Atlantic Jet - LGM

• Transition between this 2d zonal velocity and the
  zonal mean zonal velocity, on a rectangular,
  singly periodic domain

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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
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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
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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
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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
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2d Atlantic Jet - LGM

• Eddies after 45 day integration

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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

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2d Atlantic Jet - LGM

• Size of eddies by region left half vs right
  half and middle half vs edge half

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2d Atlantic Jet - LGM

• Growth by region Projection of tendency onto
  streamfunction

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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
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2d Atlantic Jet- MODERN

• Transition between this 2d zonal velocity and the
  zonal mean zonal velocity, on a rectangular,
  singly periodic domain

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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
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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
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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
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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
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2d Atlantic Jet-MODERN

• Eddies after 25 day integration- vertical tilt
  53 degrees

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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?

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2d Atlantic Jet - MODERN

• The eddy size and growth by region oscillates in
  time

Growth rate by region
Eddy size by region