LGM Seasonal Energetics

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LGM Seasonal Energetics

• October, 2009

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Annual mean insolation
Reflects Obliquity Change Only (Modern 23.45
LGM 22.95)
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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
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Insolation Changes
Solid Land average, Dotted Ocean Average
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Absorbed Solar Radiation
High Latitude summer changes dominate
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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 its 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)

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

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Atmospheres effect on ASR changeSigns are
defined such that positive mean atmos gainsLGM -
MOD
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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
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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
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Surface Changes- Land Ocean
Solid Land Domain / Dotted Ocean Domain
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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)
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SURFACE HEAT BUDGET annual mean
LGM surface LW goes up despite lower temperature-
must Be because atmos has more vapor
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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 hemispheres because
of more extensive sea-ice- NA is weird
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SURFACE HEAT FLUX LAND Domain
Positive to the atmosphere
Bottom is an order of magnitude smaller than ocean
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FS Change
LGM gets more heat from ocean in NH winter NOT
sure abour SH Land changes
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Where does the LGM atmosphere get additional
winter heat from?
MODERN
JFM FS (colors in W/m2) and sea Ice
concentration
LGM
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JFM FS change (LGM-MOD)
SEA ICE is from LGM
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JFM FS change- define regionsof interest
Composite around regions of large FS change Where
does the energy come from
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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
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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
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Global Mean Energetics

• Solid PI (CAM)/ Dashed LGM / Dotted
  Observations
• Should we be worried about model-observation
  difference?

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3 Box Surface Temp.
Elevation change in LGM is a potential
issue Larger LGM high latitude seasonal cycle
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3 Box Atmos Temp.
Elevation change in LGM is a potential
issue Slightly Larger LGM high latitude seasonal
cycle
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3 box temp- amplitudes
Seasonal Temp. Amplitude
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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
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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
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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.
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6 box energies- PI (cam) and obs
Solid observations / dashed modeled
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6-box temperatures- TS
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6-box temperatures- TV
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6 box temp amplitudes
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6-box energies- SAME LAND MASK (modern grid
boxes with gt95 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 -gt less zonal heat transport to the land -gt
  
• larger seasonal cycle over land

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6-box energies- LGM/quad-PI
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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
doesnt change much Total energy accumulated
MHT, OLR, and CTEN (quadrature) variability
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Ocean Domain Seasonal Amplitudes
Note- ASR and ZHT are in phase over ocean
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Change in non-open ocean
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Diffusive heat transportStart with zonal mean
vertically averaged temp
I interpolate Below the Topography To make A
vertically Integrated Temp record That isnt
biased By topography (I think)
MOD RED / LGM BLUE solidraw / dashed
trunc. Legendre exp. Not many zonal mean
differences beyond the global mean
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Heat transport divergence
MOD RED / LGM BLUE solidraw / dashed
trunc. Legendre exp. Not many zonal mean
differences
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Legendre Fourier expand temp and MHT_div
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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
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Back out D
Not all wavenumbers fall on a line of constant D-
BUT the 2 in the LGM and MOD do- D/a2 .98
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Reconstruct HT, from T and D
T is Truncated At wave 6
D is held constant, from the mod Wave2 fit- SH
placement is off
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Reconstruct HT from T and D
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MAX HT reconstruct
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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 R2 are .86 and
.89 for NH and SH
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B_mht from 3 box models -TS
B_MHT values vary widely between models- however
R2 values are Slightly better and .87 and .91
for NH and SH
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B_olr from 3 box model
Asterisk NH Square SH Solid
NH Linear Dashed SH Linear
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Zonal mean temperatures
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Meridional Cross Section Temp.
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Delta Meridional Cross Section Temp.
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Zonal Mean Seasonal Amplitude Temp.
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Zonal mean specific humidity(OCEAN DOMAIN ONLY)
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Delta Zonal mean specific humidity(OCEAN DOMAIN
ONLY)
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PERCENT Delta Zonal mean specific humidity(OCEAN
DOMAIN ONLY)
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Summer winter LW heating(JJA DJF NH and
DJF-JJA SH)
LW heating OPPOSSES the seasonal cycle
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Quad pi change in annual mean LW heat
In general, counters the mean state change-
convection does that
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Seasonal amplitude LW heating
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Quad PI seasonal amplitude LW