Download Heat transport during the Last Glacial Maximum in PMIP2 models

Heat transport during the Last
Glacial Maximum in PMIP2 models
January 2012
With Shih-Yu Lee
PMIP2 Models
•
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•
•
•
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CNRM T63 L45
IAP FGOALS T42 L26
HadCM3 2.5%3.8 L19
IPSL 2.5X3.75 L19
Micro3.2 (medres) T42 L20
CCSM T42 – lower resolution than the CMIP3
(I’m missing E and P fields)
• MPI ECHAM 5 (lower resolution– I don’t have a
PI run at the same resolution – Don’t use here)
Planetary albedo change and partition
Planetary albedo partitioning?
Reflected by
Atmosphere
Solar Incident
Reflected by
Surface
Atmosphere
Earth’s
Surface
Surface albedo and planetary
Calculating MHT (annual average)
• Total MHT is (ASR-OLR) integrated over the polar cap
to the latitude where the flux is calculated (the global
mean of ASR-OLR is removed so that there is no heat
transport through the poles)
• The ocean heat transport (OHT) is the surface heat
flux integrated over the polar cap (global average
removed)
• Atmospheric heat transport (AHT) is the residual: AHT
= MHT –OHT
• Atmos. Moist heat transport is L(P-E) integrated over
the polar cap (with a global average adjustment)
• Atmos. Dry heat transport is the residual: Atmos.
Dry=AHT –Atmos. Moist
• We’d like to do the stationary, mean overturning and,
transient decomposition as well
The LGM-PI difference in total (Ocean + Atmos) meridional heat transport is
smaller than the inter-model spread
Ensemble average MHT change
Solid line is the ensemble average. Shading is 1 sigma. The change in
heat transports are not significantly different from 0 (the cross-equatorial
change is)
Understanding MHT change
5.8 PW
ASR*
OLR*
8.2 PW
Heat
Transport =
2.4 PW
-
ΔMHT = ΔASR* - ΔOLR*
means
NH
ΔMHT = ΔASR* - ΔOLR*
+0.1 PW = +0.8 PW - 0.7PW
SH
-0.05 PW = -0.04 PW - 0.01 PW
ΔASR* = ΔMHT + ΔOLR*
slopes
NH
1 = 0.44 + 0.56
SH
1 = 0.45 + 0.55
(regress against Δ ASR* spread)
Dominant balance is
between ASR* and OLR* !
TheWhat
surface
and
atmospheric
reflection
determines ΔASR*?
contributions
to ASR*
Reminder:
partitioning in modern
climate.
ASR* change (surface and atmos. Components)
ΔASR*
means
ΔASR*SURF + ΔASR*CLOUD + incident
NH
+0.8 PW = +1.12 PW
-
SH
-0.04 PW = +0.15 PW
- 0.18 PW
ΔASR*
slopes
=
0.37PW
=
ΔASR*SURF + ΔASR*CLOUD + incident
NH
1
=
0.22
+
0.77
+ 0.01
SH
1
=
0.66
+
0.38
-0.04
+ 0.05PW
-
0.01 PW
Ensemble mean ΔASR* is due to surface albedo change. Spread in the NH is due
to cloud response differences.
Ensemble average MHT change
Solid line is the ensemble average. Shading is 1 sigma. The change in
heat transports are not significantly different from 0 (the cross-equatorial
change is)
MHT change and ocean/atmos contributions
ΔMHT
means
ΔAHT
+
ΔOHT
NH
+0.1 PW = +0.24 PW
- 0.14PW
SH
-0.04 PW = 0.0 PW
- 0.04 PW
NH
slopes
=
SH
ΔMHT =
ΔAHT
1
0.20
=
+
+
ΔOHT (regress vs. MHT)
0.80
1
= 0.75
+ 0.25
Ocean atmos. Compensation R^2 is 0.40 in the NH and 0.70 in SH
Ensemble average AHT change
Solid line is the ensemble average. Shading is 1 sigma. The trade off between moist
and dry AHT is robust across models (moisture transport goes down in the LGM). At
the equator the changes are consistent with Northward cross equatorial heat transport
by the Hadley cell (with the moisture transport opposing the net heat transport)
AHT change and moist/dry contributions
ΔAHT
means
Δdry
+
Δmoist
NH
+0.1 PW = +0.27 PW
- 0.17PW
SH
-0.1 PW = 0.14 PW
- 0.24 PW
ΔMHT =
slopes
=
Δdry
+
Δmoist (regress vs. AHT)
NH
1
=
1.16
-
0.16
SH
1
=
0.60
+
0.40
AHT #s are
different cause
CCSM is
excluded here
Cross equatorial heat transport
• Cross equatorial MHT (atmos + ocean) is half the
hemispheric difference in ASR (SH – NH) – the
hemispheric difference in OLR (SH-NH)
• MHTEQ= (ASRSH - ASRNH )/2 - (OLRSH - OLRNH )/2
• MHTEQ = <ASR> - <OLR>
<ASR>
SH
<ASR>
<OLR>
<OLR>
MHTEQ
NH
ΔMHTeq , Δ<ASR> and, Δ<OLR>
Robust increase in cross equatorial total heat transport due to <ASR> change
MHTEQ, AHTEQ and OHTEQ
ITCZ change
ITCZ intensity change and AHTEQ
Change in Annual mean surface temp
Colors are the ensemble mean change
Contours are the inter-model spread with contour interval 2k
Precipitation change
Contours are precipitation in the PI climatology
Seasonal precipitation changes
Seasonal Cycle of Surface Temp.
Contours are inter-model spread with contour interval 2K
Seasonal Heating
Seasonal Heating Climatology
LGM change in seasonal heating
Less water vapor and more topography (thinner atmosphere) leads to less
Shortwave atmospheric absorption
Change in seasonal surface fluxes
More sea ice insulates the system from the heat capacity of the ocean leading
To larger seasonal energy fluxes to the atmosphere
Land ice has high albedo -> less seasonal energy input to the atmosphere
Seasonal surface flux change
and ice change
Zonal average change in
seasonal heating
Change in seasonal amplitude of temperature
EXTRAS
MHT and partition change in each model
Same data- grouped by circulation classes
The only robust changes across the models is the decreased moist transport
and increased dry transport
Does the change in ocean heat
transport predict the change in AHT?
Climatological seasonal
amplitude of temperature