Atlantic Jet: Stability of jet core

1. Atlantic Jet:Stability 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