Atlantic Jet Stability of jet core Thermal winds

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 700 hpa

Modern 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 stabilitystructure 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-atlantic Modern normal mode growth rates are Western Atlantic = 3. 7 * 10 ^ -6 Mid Atlantic = 2. 6 *10 ^ -6

Seeding the mid-atlantic LGM normal mode growth rates are Western Atlantic = 5. 9 * 10 ^ -6 Mid Atlantic = 4. 65 *10 ^ -6

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

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

2 d 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

2 d 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

2 d 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

2 d 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

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

2 d 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

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

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

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

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

2 d 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

2 d 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

2 d 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

2 d 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

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

2 d 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?

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