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LGM Seasonal Energetics

LGM Seasonal Energetics. October, 2009. Annual mean insolation. Reflects Obliquity Change Only (Modern = 23.45 LGM = 22.95). TOA seasonal incoming Insolation. Primarily reflects obliquity (precession change from 102 in modern to 114 in LGM), biggest high latitude effect in summer.

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LGM Seasonal Energetics

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  1. LGM Seasonal Energetics October, 2009

  2. Annual mean insolation Reflects Obliquity Change Only (Modern = 23.45 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 changeSigns are defined such that positive mean atmos gainsLGM - 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 regionsof interest Composite around regions of large FS change Where does the energy come from

  22. Composite FS seasonal cyclesNorth 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 transportStart 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 Linear

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