Download - Atlantic Jet: Stability of jet core
Atlantic Jet:Stability of jet core
Thermal winds between 930 and 430 hpa
Look at cross sections where the baroclinicity is greatest – those
positions are
Velocity in Cross section-Northern Hemisphere
Temperature in cross section-700hpa
Modern Stability
Modern Stability
LGM Stability
LGM Stability
Mid Atlantic Jet• Look at jet stability at location of greatest barotropic shear at 800 hpa
Mid Atlantic Jet• Also consider vorticity gradient
Find location of max shear and vorticity gradient in LGM
Minnimum vorticity gradient
Maximum Velocity Shear
Cross sections of zonal velocity at location of maximum velocity shear
Mid atlantic modern stability- structure of eddy
Mid atlantic modern stability- Growth by layer
Mid atlantic LGM stability- Structure of Eddy
Mid atlantic LGM stability- Growth by layer
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)
Seeding the mid-atlanticModern normal mode growth rates areWestern Atlantic = 3.7 * 10 ^ -6Mid Atlantic = 2.6 *10 ^ -6
Seeding the mid-atlanticLGM normal mode growth rates areWestern Atlantic = 5.9 * 10 ^ -6Mid Atlantic = 4.65 *10 ^ -6
2d Atlantic jet -LGM• Define a domain over which the thermal wind between
900 hPa and 400 hPa is above a threshold value.
LGM
2d Atlantic Jet - LGM• Transition between this 2d zonal velocity and the zonal mean zonal
velocity, on a rectangular, singly periodic domain
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
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
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
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
2d Atlantic Jet - LGM• Eddies after 45 day integration
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
0 0.5 1 1.5 2 2.5 3
x 106
2
4
6
8
10
12
14
layer 1 datalayer 1 fit slope = 3.4849e-006layer 3 datalayer 3 fit slope =3.4958e-006spatial growth == 3.5134e-006+3.537e-006i
2d Atlantic Jet - LGM• Size of eddies by region – left half vs right half and middle half vs edge half
0 0.5 1 1.5 2 2.5 3
x 106
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5Ratio of eddy activity in different parts of the domain as a function of time
time (hours)
ratio
n of
sta
ndar
d de
viat
ions
Layer 1 ratio of left to rightLayer 1ratio of middle to edgeLayer 3 ratio of left to rightLayer 3 ratio of middle to edge
2d Atlantic Jet - LGM• Growth by region – Projection of tendency onto streamfunction
2d Atlantic jet - MODERN• Define a domain over which the thermal wind between
900 hPa and 400 hPa is above a threshold value.
MODERNMODERN
2d Atlantic Jet- MODERN• Transition between this 2d zonal velocity and the zonal mean zonal
velocity, on a rectangular, singly periodic domain
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
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
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
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
2d Atlantic Jet-MODERN• Eddies after 25 day integration- vertical tilt = 53 degrees
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?
0 1 2 3 4 5 6
x 106
0
2
4
6
8
10
12
14
16
18
layer 1 datalayer 1 fit slope = 2.8619e-006layer 3 datalayer 3 fit slope =2.8497e-006spatial growth == 2.3347e-006+2.7205e-006i
2d Atlantic Jet - MODERN• The eddy size and growth by region oscillates in time
Growth rate by region Eddy size by region
0 1 2 3 4 5 6
x 106
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2Ratio of eddy activity in different parts of the domain as a function of time
time (hours)
ratio
n of
sta
ndar
d de
viat
ions
Layer 1 ratio of left to rightLayer 1ratio of middle to edgeLayer 3 ratio of left to rightLayer 3 ratio of middle to edge