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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. - PowerPoint PPT Presentation
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TOA seasonal incoming Insolation
Primarily reflects obliquity (precession change from 102 in modern to 114 in LGM), biggest high latitude effect in summer
ASR by components
• Delta_ASR = delta_Incoming + delta_surface_net + delta_atmosphere_net
• we have delta_surface_sw– presumably this associated with a surface albedo change
• We also have delta incomin• Therefore delta_atmosphere =
delta_SW_net_TOA – delta_incoming –delta_surface_sw_net
• Can’t say if this is due to a change in atmospheric albedo or atmospheric absorption of SW
ASR by components
Solid = incoming / Dashed = surface / dotted = atmosphere
Surface albedo chnages in the mid-latitude summer dominate
Atmospheric ASR changes/ Land-Sea
Solid = Land /Dotted = OceanNote; this is atmos contribution to total ASR, not ASR in the atmosNecessarily (could be atmos albedo change)
SURFACE HEAT BUDGET annual mean
LGM surface LW goes up despite lower temperature- mustBe because atmos has more vapor
SURFACE HEAT FLUX – OCEAN Domain
Positive = to the atmosphere- LGM has smaller seasonal heat fluxIn both hemisphere’s because of more extensive sea-ice- NA is weird
Bottom Plot TakesInto AccountChange inLand FracIn LGM
SURFACE HEAT FLUX – LAND Domain
Positive = to the atmosphere Bottom is an order of magnitude smaller than ocean
Where does the LGM atmosphere get additional winter heat from?
JFM FS (colors inW/m^2) and sea Ice concentration
MODERN
LGM
JFM FS change- define regionsof interest
Composite around regions of large FS changeWhere does the energy come from
Composite FS seasonal cyclesNorth Atlantic Regions
Each region changes its annual mean FS- consequence of uncoupledRun? Are there really large ocean heat transport changes
North Atlantic Feb. FS and TS
Solid = Modern, Dashed = LGMSea ice edge has large FS gradient, leads to large temp. gradTemp. grad reverses north of Ice edge
Global Mean Energetics
Solid = PI (CAM)/ Dashed = LGM / Dotted = Observations
Should we be worried about model-observation difference?
3 Box Surface Temp.
Elevation change in LGM is a potential issueLarger LGM high latitude seasonal cycle
3 Box Atmos Temp.
Elevation change in LGM is a potential issueSlightly Larger LGM high latitude seasonal cycle
3-BOX_Energies
SOLID = MODERN / DASHED = LGMLGM polar region has less seasonality in ASR (albedo is higher) but Equally large changes in FS
3 BOX energy changes (LGM-MOD)
SH has smaller ASR amplitude but even smaller MHT variability, so the OLR and MHT amplitude upNH Summer changes dominate
(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.
6-box energies- **SAME LAND MASK** (modern grid boxes with >95% LFRAC)
LGM = dashed/ MOD =SolidLess 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
Land Domain Seasonal Amplitudes
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 muchTotal energy accumulated = MHT, OLR, and CTEN (quadrature) variability
ZHTTo landIs outOf phaseWith ASR
Diffusive heat transportStart with zonal mean vertically averaged temp
MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp.Not many zonal mean differences beyond the global mean
I interpolateBelow the TopographyTo makeA verticallyIntegratedTemp record That isn’t biasedBy topography(I think)
Heat transport divergence
MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp.
Not many zonal mean differences
LGM –MOD legendre four. Coef.s
Stronger annual mean temp. grad. In LGM. Seasonal changes are moreComplex; Annual mean heat flux changes also up in LGM
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
Reconstruct HT, from T and D
D is held constant, from the mod Wave#2 fit- SH placement is off
T isTruncatedAt wave#6