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Heat transport during the Last Glacial Maximum in PMIP2 models January 2012 With Shih-Yu Lee PMIP2 Models • • • • • • 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