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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.

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annual mean insolation
Annual mean insolation

Reflects Obliquity Change Only (Modern = 23.45 LGM = 22.95)

toa seasonal incoming insolation
TOA seasonal incoming Insolation

Primarily reflects obliquity (precession change from 102 in modern

to 114 in LGM), biggest high latitude effect in summer

insolation changes
Insolation Changes

Solid = Land average, Dotted = Ocean Average

absorbed solar radiation
Absorbed Solar Radiation

High Latitude summer changes dominate

asr by components
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 components1
ASR by components

Solid = incoming / Dashed = surface / dotted = atmosphere

Surface albedo chnages in the mid-latitude summer dominate

surface changes land ocean
Surface Changes- Land Ocean

Solid = Land Domain / Dotted = Ocean Domain

atmospheric asr changes land sea
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)

surface heat budget annual mean

LGM surface LW goes up despite lower temperature- must

Be because atmos has more vapor

surface heat flux ocean domain


Plot Takes

Into Account

Change in

Land Frac


Positive = to the atmosphere- LGM has smaller seasonal heat flux

In both hemisphere’s because of more extensive sea-ice- NA is weird

surface heat flux land domain

Positive = to the atmosphere

Bottom is an order of magnitude smaller than ocean

fs change
FS Change

LGM gets more heat from ocean in NH winter

NOT sure abour SH Land changes

where does the lgm atmosphere get additional winter heat from
Where does the LGM atmosphere get additional winter heat from?


JFM FS (colors in

W/m^2) and sea

Ice concentration


jfm fs change lgm mod
JFM FS change (LGM-MOD)

SEA ICE is from LGM

jfm fs change define regions of interest
JFM FS change- define regionsof interest

Composite around regions of large FS change

Where does the energy come from

composite fs seasonal cycles north atlantic regions
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

north atlantic feb fs and ts
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

global mean energetics
Global Mean Energetics

Solid = PI (CAM)/ Dashed = LGM / Dotted = Observations

Should we be worried about model-observation difference?

3 box surface temp
3 Box Surface Temp.

Elevation change in LGM is a potential issue

Larger LGM high latitude seasonal cycle

3 box atmos temp
3 Box Atmos Temp.

Elevation change in LGM is a potential issue

Slightly Larger LGM high latitude seasonal cycle

3 box energies


LGM polar region has less seasonality in ASR (albedo is higher) but

Equally large changes in FS

3 box energy changes lgm mod
3 BOX energy changes (LGM-MOD)

SH has smaller ASR amplitude but even smaller MHT variability, so the OLR and MHT amplitude up

NH 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 pi cam and obs
6 box energies- PI (cam) and obs

Solid = observations / dashed = modeled

6 box energies same land mask modern grid boxes with 95 lfrac
6-box energies- **SAME LAND MASK** (modern grid boxes with >95% LFRAC)

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

land domain seasonal amplitudes
Land Domain Seasonal Amplitudes


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

ocean domain seasonal amplitudes
Ocean Domain Seasonal Amplitudes

Note- ASR and ZHT are in phase over ocean

diffusive heat transport start with zonal mean vertically averaged temp
Diffusive heat transportStart with zonal mean vertically averaged temp

I interpolate

Below the


To make

A vertically


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

heat transport divergence
Heat transport divergence

MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp.

Not many zonal mean differences

lgm mod legendre four coef s
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

back out d
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
Reconstruct HT, from T and D

T is


At wave#


D is held constant, from the mod Wave#2 fit- SH placement is off