1. LGM Seasonal Energetics
October, 2009

2. Annual mean insolation
Reflects Obliquity Change Only (Modern = LGM = 22.95)

3. TOA seasonal incoming Insolation
Primarily reflects obliquity (precession change from 102 in modern
to 114 in LGM), biggest high latitude effect in summer

4. Insolation Changes
Solid = Land average, Dotted = Ocean Average

5. Absorbed Solar Radiation
High Latitude summer changes dominate

6. ASR by components ASR = Incoming_SW – outgoing_SW
Outgoing = what never makes it surface + reflected by surface + residual
What never makes it to surface = downwelling_TOA – downwelling_Surf---- this could be absorbed or reflected but lets assume it’s reflected by atmos
reflected by surface = upwelling_Surf
Res = up_TOA - what never makes it surface – upwelling surface
The residual includes the absorbed (and scattered) downwelling and the upwelling radiation that is absorbed, reflected in the atmos (res = approx. 20% incoming, fairly spatially uniform)

7. ASR by components- all signs are gain to atmosphere
Solid = incoming / Dashed = surface / dotted = atmosphere
Dashed dot are residual (small)

8. ASR by components- all signs are gain to atmosphere
Solid = NET (all terms) / Dashed = surface albedo / dotted = atmosphere
Large but not total compensation between the atmos and surface

9. What never makes it to surface (atmos) by components
Total = downwelling_TOA – downwelling_Surf
Clear = downwelling_TOA –down_SURF_clear
Cloudy = down_SURF_clear – down_Surf

10. Atmosphere’s effect on ASR change Signs are defined such that positive mean atmos gains LGM - MOD

11. More clouds = more reflection
July LGM – MOD
Cloud liquid water (vert. Int. in kg) change
July- LGM - MOD
Change in radiation REFLECTED
(+ = more LGM up) SW

12. More clouds = more reflection
JAN LGM – MOD
Cloud liquid water (vert. Int. in kg) change
JAN- LGM - MOD
Change in radiation REFLECTED
(+ = more LGM up) SW
Cloud changes could be multiplied by incoming solar to try
And tease out the change in reflected--- if we care

13. Surface Changes- Land Ocean
Solid = Land Domain / Dotted = Ocean Domain

14. Atmospheric ASR changes/ Land-Sea
Solid = Land /Dotted = Ocean
Note; this is atmos contribution to total ASR, not ASR in the atmos
Necessarily (could be atmos albedo change)

15. SURFACE HEAT BUDGET annual mean
LGM surface LW goes up despite lower temperature- must
Be because atmos has more vapor

16. SURFACE HEAT FLUX – OCEAN Domain
Bottom
Plot Takes
Into Account
Change in
Land Frac
In LGM
Positive = to the atmosphere- LGM has smaller seasonal heat flux
In both hemisphere’s because of more extensive sea-ice- NA is weird

17. SURFACE HEAT FLUX – LAND Domain
Positive = to the atmosphere
Bottom is an order of magnitude smaller than ocean

18. FS Change LGM gets more heat from ocean in NH winter
NOT sure abour SH Land changes

19. Where does the LGM atmosphere get additional winter heat from?
MODERN
JFM FS (colors in
W/m^2) and sea
Ice concentration
LGM

20. JFM FS change (LGM-MOD)
SEA ICE is from LGM

21. JFM FS change- define regions of interest
Composite around regions of large FS change
Where does the energy come from

22. Composite FS seasonal cycles North Atlantic Regions
Each region changes its annual mean FS- consequence of uncoupled
Run? Are there really large ocean heat transport changes

23. North Atlantic Feb. FS and TS
Solid = Modern, Dashed = LGM
Sea ice edge has large FS gradient, leads to large temp. grad
Temp. grad reverses north of Ice edge

24. Global Mean Energetics
Solid = PI (CAM)/ Dashed = LGM / Dotted = Observations
Should we be worried about model-observation difference?

25. 3 Box Surface Temp. Elevation change in LGM is a potential issue
Larger LGM high latitude seasonal cycle

26. 3 Box Atmos Temp. Elevation change in LGM is a potential issue
Slightly Larger LGM high latitude seasonal cycle

27. 3 box temp- amplitudes
Seasonal
Temp.
Amplitude

28. 3-BOX_Energies SOLID = MODERN / DASHED = LGM / Dotted = 4 X co2
LGM polar region has less seasonality in ASR (albedo is higher) but
Equally large changes in FS

29. 3 BOX energy changes (LGM/quad-PI)
LGM – PI
Is SOLID
Quad – PI
Is dashed
SH has smaller ASR amplitude but even smaller MHT variability, so the OLR and MHT amplitude up
NH Summer changes dominate

30. 3 box seasonal amplitudes
(ASR-FS) is the energy fluxed to the atmosphere. Seasonal cycle ASR goes down in the LGM(enhanced albedo) but so does FS, so the energy fluxed to the atmosphere is unchanged. The partitioning of that energy between OLR and MHT is interesting.

31. 6 box energies- PI (cam) and obs
Solid = observations / dashed = modeled

32. 6-box temperatures- TS

33. 6-box temperatures- TV

34. 6 box temp amplitudes

35. 6-box energies- **SAME LAND MASK** (modern grid boxes with >95% LFRAC)
Solid =PI
Dashed = LGM
Dotted = quad
LGM = dashed/ MOD =Solid
Less energy into LGM Ocean = more energy into LGM atmos over ocean = larger temp variability over ocean -> less zonal heat transport to the land ->
larger seasonal cycle over land

36. 6-box energies- LGM/quad-PI

37. Land Domain Seasonal Amplitudes
ZHT
To land
Is out
Of phase
With ASR
Less LGM ASR cycle- but less energy is exported zonally because ocean temps. Have a larger seasonal cycle. The energy accumulated over land doesn’t change much
Total energy accumulated = MHT, OLR, and CTEN (quadrature) variability

38. Ocean Domain Seasonal Amplitudes
Note- ASR and ZHT are in phase over ocean

39. Change in non-open ocean

40. Diffusive heat transport Start with zonal mean vertically averaged temp
I interpolate
Below the
Topography
To make
A vertically
Integrated
Temp record
That isn’t biased
By topography
(I think)
MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp.
Not many zonal mean differences beyond the global mean

41. Heat transport divergence
MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp.
Not many zonal mean differences

42. Legendre Fourier expand temp and MHT_div

43. LGM –MOD legendre four. Coef.s
Stronger annual mean temp. grad. In LGM. Seasonal changes are more
Complex; Annual mean heat flux changes also up in LGM

44. Back out D
Not all wavenumbers fall on a line of constant D- BUT the #2 in the
LGM and MOD do- D/a^2 = .98

45. Reconstruct HT, from T and D
T is
Truncated
At wave# 6
D is held constant, from the mod Wave#2 fit- SH placement is off

46. Reconstruct HT from T and D

47. MAX HT reconstruct

48. B_mht from 3 box models - TV
B_MHT values are 3 +/- .4 (2 sigma) and 2 +/-.1 for NH and SH
We used 3.4 in EBM; R^2 are .86 and .89 for NH and SH

49. B_mht from 3 box models -TS
B_MHT values vary widely between models- however R^2 values are
Slightly better and = .87 and .91 for NH and SH

50. B_olr from 3 box model Asterisk =NH Square = SH Solid = NH Linear
Dashed = SH