Arctic clouds, circulation, and sea ice during 2007 and beyond

Processes Controlling21st Century Southern OceanClimate-Cloud FeedbacksJen KayBrian Medeiros, Andrew GettelmanNCAR CGD AMPThanks to Lorenzo Polvani and Cecilia Bitz1Image from: http://photolibrary.usap.gov/Portscripts/PortWeb.dll?query&field1=Filename&op1=matches&value=ICEBERG11.JPG&catalog=Antarctica&template=USAPgovMidThumb

Zonal annual mean cloud distributionCloudSat+CALIPSO observations, combined as in Kay and Gettelman (2009)Southern Ocean30-70 SouthClouds are tracers for the global-scale atmospheric circulation. Can see the poleward summertime and equatorward wintertime movement of the stormtrack.Winter hemisphere has stronger subsidence and fewer clouds through the troposphere.Equatorward flank influenced by sub-tropical processes (subsidence) Poleward flank influenced by polar processes (sea ice)2Why study Southern Ocean clouds?

Gettelman, Kay, and Shell (2012)Southern ocean research questions 1) Which processes control climate-cloud feedbacks over the Southern Ocean (30-70 S)?2) Are the model processes controlling these feedbacks realistic? Are there observational constraints?3) How do Southern Ocean climate-cloud feedbacks affect the global climate system?Large gradients in magnitude and sign (CESM-CAM5) for cloud feedbacks over the Southern Ocean.3Today transient CESM-CAM5 21st century runs with RCP8.5 forcing

Meinshausen et al. 2011

Lamarque et al. 20112.5x increase in the CO2 equivalence.

Meinshausen, M., S. J. Smith, K. V. Calvin, J. S. Daniel, M. L. T. Kainuma, J.-F. Lamarque, K. Matsumoto, S. A. Montzka, S. C. B. Raper, K. Riahi, A. M. Thomson, G. J. M. Velders and D. van Vuuren (2011). "The RCP Greenhouse Gas Concentrations and their Extension from 1765 to 2300." Climatic Change (Special Issue), DOI: 10.1007/s10584-011-0156-z

CO2EQ - (For Information only, not CMIP5 recommendation) CO2 equivalence concentrations using CO2 radiative forcing relationship Q = 3.71/ln(2)*ln(C/278), aggregating all (efficacy-adjusted) anthropogenic forcings, including greenhouse gases listed below (i.e. columns 3,4,5 and 8-35), and aerosols, trop. ozone etc. (not listed below).

Lamarque, J.-F., G. P. Kyle, M. Meinshausen. K. Riahi, S. J. Smith, D. P. van Vuuren, A. Conley, F. Vitt. Global and regional evolution of short-lived radiatively-active gases and aerosols in the Representative Concentration Pathways. Climatic Change, doi:10.1007/s10584-011-0155-0, 2011.

From Lamarque et al. 2011. All RCPs have similar emission and concentration trajectories for ozone depleting substances (except N20) so all else being equal they should have the same stratospheric ozone trajectory but chemistry-climate coupling changes the distribution of ozone but ozone recovery/increases are larger in RCP8.5 and even exceed 1850 values!4

Zonal Mean Optical Depth ChangesLarge changes and large gradients. Juicier clouds!21st century cloud changes resemble 2xCO2 cloud feedbacks5

OUTLINE:Processes affecting 21st C Southern Ocean cloud-climate changes1) Antarctic sea ice loss2) Large-scale atmospheric circulation shifts (dynamics)3) Warming (thermodynamics)II. Summary and ongoing workSouthern ocean research questions 1) Which processes control climate-cloud feedbacks over the Southern Ocean (30-70 S)?2) Are the model processes controlling these feedbacks realistic? Are there observational constraints?3) How do Southern Ocean climate-cloud feedbacks affect the global climate system?

Photo from National Geographic6PROCESS #1: Antarctic sea ice loss

1950-2005. Weak increases in observed extent. CESM-CAM5 has decreases in extent.RCP8.5 Large decreases in Antarctic sea ice by 2080-2099.7Change over 21st century

CESM Vertical cloud structureCloud response to Antarctic sea ice lossEarly 21st centuryRaising of the cloud base8Distinct 21st century cloud changes where Antarctic sea ice loss occurs

Low cloud increases in MAM (SH Fall). In contrast to non-sea ice loss regions where low cloud fraction is decreasing.Larger LWP increases than in non-sea ice loss regionsIWP increases. In contrast to IWP decreases in other regions.

Cloud response to sea ice loss = Fall cloud increases, larger increases in LWP and IWP

TO DO: Plot vertical structure of CLDLIQ, CLDICE, CLOUD, T, RH in regions that become ice free over the 21st century.Do it by season.9PROCESS #2: Large-scale atmospheric circulation shifts20th C = poleward SH stormtrack shiftO3 (GHG )Thompson et al. 2011

21st C = poleward SH stormtrack shift GHG (despite O3 )Ozone depletion/GHG increases cause stratospheric cooling/tropospheric warming/poleward shift of storm track. Ozone recovery opposite.+Std = +SAM = poleward shift.

Thompson, D.W.J., S. Solomon, P.J. Kushner, M.H. England, K.M. Grise and D.J. Karoly, 2011: Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change. Nature Geoscience. doi:10.1038/ngeo1296.

NOTE: Observed shift greater than the modeled shift for reasons that remain unknown. Missing forcing?

Johanson, C. M. and Q. Fu, 2009: Hadley cell widening: Model simulations versus observations. J. Climate, 22, 27132725. Observations show that the Hadley cell has widened by about 25 since 1979. This widening and the concomitant poleward displacement of the subtropical dry zones may be accompanied by large-scale drying near 30N and 30S. Such drying poses a risk to inhabitants of these regions who are accustomed to established rainfall patterns. Simple and comprehensive general circulation models (GCMs) indicate that the Hadley cell may widen in response to global warming, warming of the west Pacific, or polar stratospheric cooling. The combination of these factors may be responsible for the recent observations. But there is no study so far that has compared the observed widening to GCM simulations of twentieth-century climate integrated with historical changes in forcings. Here the Hadley cell widening is assessed in current GCMs from historical simulations of the twentieth century as well as future climate projections and preindustrial control runs. The authors find that observed widening cannot be explained by natural variability. This observed widening is also significantly larger than in simulations of the twentieth and twenty-first centuries. These results illustrate the need for further investigation into the discrepancy between the observed and simulated widening of the Hadley cell.

Yin, J. H. (2005), A consistent poleward shift of the storm tracks in simulations of 21st century climate, Geophys. Res. Lett., 32, L18701, doi:10.1029/2005GL023684.

A consistent poleward and upward shift and intensification of the storm tracks is found in an ensemble of 21st century climate simulations performed by 15 coupled climate models. The shift of the storm tracks is accompanied by a poleward shift and upward expansion of the midlatitude baroclinic regions associated with enhanced warming in the tropical upper troposphere and increased tropopause height. The poleward shift in baroclinicity is augmented in the Southern Hemisphere and partially offset in the Northern Hemisphere by changes in the surface meridional temperature gradient. The poleward shift of the storm tracks also tends to be accompanied by poleward shifts in surface wind stress and precipitation, and a shift towards the high index state of the annular modes. These results highlight the integral role that the storm tracks play in the climate system, and the importance of understanding how and why they will change in the future.10Change over 21st century

Zonal mean SH CESM Circulationtop=early 21st C, bottom=21st C changeStronger WesterliesIncreased subsidenceEarly 21st centuryTop row = avg(2006-2025), Bottom row = avg(2080-2099) avg(2006-2025)

CESM has an intensification of the westerly winds and increased subsidence poleward stormtrack shift/+SAM.

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CESM clouds respond to increased subsidence over the 21st CenturyCloud fraction decreases except near the surfaceCloud decreases in both subsidence and upsidence regimes, except near the surface.1221st Century zonal mean total cloud fraction changes by season

Cloud decreases (subsidence increases) are larger in winter than in summer.Interesting that there is a larger cloud decrease during SH winter Larger subsidence increases during winter as well so this all hangs together ok.

But we have to know more than cloud fraction to understand radiative impacts. SO NEXT Beyond cloud fraction!!13PROCESS #3: ThermodynamicsZonal mean change shows both a poleward shift and larger maximum cloud liquid water path.

How do we separate the influence of dynamics and thermodynamics on these cloud changes?dynamic influence = poleward shift of the storm trackthermodynamic influence = change in cloud liquid water content for a given circulation condition.14 Bonygrams can separate the dynamic and thermodynamic components of tropical cloud changesBony et al. 2004, Climate Dynamics

AscentDescent

AscentDescent15

Bonygrams for the Southern Ocean?

Thermodynamics in stormtracks explains juicier clouds-30 S to -70 S, >650 mb.

Smoking gun is that the subsidence occurrence frequency (top panel) changes less than the cloud liquid water content at a given subsidence.

16Juicier warm clouds, more often

ColdWarmBonygrams with Temperature?-30 S to -70 S, >650 mb

Separating thermodynamics and dynamics by looking at changes at a constant temperature. The question here is at the same temperature how are clouds different in the early and late 21st century?

Overall warm clouds (clouds with temperatures above 273 K) have larger liquid water contents in the late 21st century than in the early 21st century.In contrast, cold clouds (clouds with temperatures below 273) are not changing or have less liquid water content the late 21st century than in the early 21st century.

If we just look at the subsidence regime (OMEGA > 0), temperatures tend to be higher as expected as this is the sub-tropics. In the subsidence regime, clouds with temperatures greater than ~280 Khave larger liquid water contents in the late 21st century than in the early 21st century. These are the low clouds in the sub-tropics.

If we just look at the upsidence regime (OMEGA < 0), the changes look very similar to the entire -30 to -70 S domain. Does this make sense?

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Is subsidence the best sorting variable to understand cloud changes?

CLDLIQ shift is not really expressed in OMEGA.Poleward stormtrack shift is seen mostly in U not OMEGA. Clouds care more about OMEGA than U evaporation isnt changing much and stronger westerly winds dont seem to affect clouds.18SummaryCESM Southern Ocean cloud-climate feedbacks vary in magnitude and sign: cooling near the Antarctic continent, warming on the equatorward flank of the mid-latitude stormtrack.Over the 21st century, projected Antarctic sea ice loss, a poleward stormtrack shift, and thermodynamic changes all contribute to Southern Ocean cloud-climate feedbacks.Juicier clouds, more often explained by thermodynamic changes.Work is ongoing. Suggestions very welcome!Comments:1) How robust are these responses in other climate models?2) The size of the ice and liquid particles is also really important not just the liquid or ice water path. Yes. I need to save more sophisticated diagnostics to look at this.3) Could you observe these changes? Possibly we have been discussing that with Helene. What type of observing platform would you need to detect these cloud changes?4) Kerguelen Island Research here at LGGE. 4921S 7013E. Talk= 10 am on Friday! There is an ice cap there that is decreasing in size not due to warming but due to less precipitation. Could this be what is expected into the future?

19Southern Ocean = cloudiest place on Earth

Southern Ocean30-70 SouthCALIPSO spaceborne lidar observations (CALIPSO-GOCCP).Southern Ocean (~30-70 S) interesting region because cloudiest place on earth southern hemisphere storm track very active year round.

20Zonal mean atmospheric circulation and cloud distributionCloudSat+CALIPSO observations, combined as in Kay and Gettelman (2009)

Southern Ocean30-70 SouthClouds are tracers for the global-scale atmospheric circulation. Can see the poleward summertime and equatorward wintertime movement of the stormtrack.Winter hemisphere has stronger subsidence and fewer clouds through the troposphere.Equatorward flank influenced by sub-tropical processes (subsidence) Poleward flank influenced by polar processes (sea ice)21Seasonal storm track shifts affect cloud location/amount

Southern Hemisphere Winter (JJA)Southern Hemisphere Summer (DJF)CloudSat+CALIPSO observations, combined as in Kay and Gettelman (2009)We know that the seasonal movement of the storm track has a profound influence on cloud distributions but the seasonal large-scale atmospheric changes are driven by much larger forcing than the 21st century LS atm changes, which are driven by ozone and greenhouse gases. Still.. Is there a potential analogue here?

Note there is stronger subsidence in the winter hemisphere and associated cloud decreases!!22Influence of stormtrack variability on the Southern Ocean in a long model control run

Hall and Visbeck (2002)+SAM = poleward shift.

Hall A, Visbeck M (2002) Synchronous variability in the southern hemisphere atmosphere, sea ice, and ocean resulting from the annular mode. J Clim. 15: 3043-3057.

23Southern Ocean cloud biases affect tropical precipitation biases!!Hwang and Frierson 2013

Observed Precipitation

Climate Model PrecipitationUpper left shows historical rainfall, and upper right is an average of climate models estimates notice the longer blue and red rain bands south of the equator. Lower left is the observed effect of low-level clouds, and lower right is the difference between the measurements and the average model output.

Hwang, Y.-T. and D. M. W. Frierson. A link between the double intertropical convergence zone problem and cloud biases over the Southern Ocean.^ in press, Proc. Nat. Acad. Sci.

If this is true Does that mean that changes in the Southern Ocean heat absorption will affect tropical precipitation???? Wow, I want to talk to Dargan/Ting about this.24

Early 21st C Zonal Annual MeansWhich processes affect 21st century Southern Ocean climate feedbacks?Introduce the zonal annual mean plots describe them well so that later in the talk they are more easily digested.25CESM has too much sea iceand thus likely too much sea ice loss

CESM Historical Sea Ice BiasCESM RCP8.5 Sea Ice LossWhat is the climate response to Antarctic sea ice loss in CESM?Bias compared to SSMI/SMRR observations late 20th century CESM run years 1981-2000.2621st century Southern Ocean clouds top=early 21st C, bottom=21st C change

Top row = avg(2006-2025) Bottom row = avg(2080-2099) avg(2006-2025)27OMEGA JJA vs. DJF

CLOUD: JJA vs. DJF

CLDLIQ change and mean T

F(T) CLDLIQ-30 S to -70 S-30 S to -40 S-40 S to -50 S-50 S to -60 S-60 S to -70 S

Separating thermodynamics and dynamics by looking at changes at a constant temperature31

F(T) CLDLIQSubsidence (OMEGA > 0)Upsidence (OMEGA < 0)-30 S to -70 S, >650 mb

Separating thermodynamics and dynamics by looking at changes at a constant temperature. The question here is at the same temperature how are clouds different in the early and late 21st century?

Overall warm clouds (clouds with temperatures above 273 K) have larger liquid water contents in the late 21st century than in the early 21st century.In contrast, cold clouds (clouds with temperatures below 273) are not changing or have less liquid water content the late 21st century than in the early 21st century.

If we just look at the subsidence regime (OMEGA > 0), temperatures tend to be higher as expected as this is the sub-tropics. In the subsidence regime, clouds with temperatures greater than ~280 Khave larger liquid water contents in the late 21st century than in the early 21st century. These are the low clouds in the sub-tropics.

If we just look at the upsidence regime (OMEGA < 0), the changes look very similar to the entire -30 to -70 S domain. Does this make sense?

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F(T) CLOUDSubsidence (OMEGA > 0)Upsidence (OMEGA < 0)-30 S to -70 S, >650 mbSeparating thermodynamics and dynamics by looking at changes at a constant temperature33

F(U) CLOUD, CLDLIQ-30 S to -70 S, >650 mbSubsidence (OMEGA > 0)Upsidence (OMEGA < 0)

34Liquid and Ice tendencies

Today CESM-CAM5 21st century runs with RCP8.5 forcing

Meinshausen et al. 2011

Lamarque et al. 2011RCP8.5 forcingavg(2006-2025)avg(2080-2099)CO2 equivalence465 ppm1162 ppm (2.5x)Stratospheric O3 (anomaly from 1850)-9 Dobson Units+5 Dobson UnitsMeinshausen, M., S. J. Smith, K. V. Calvin, J. S. Daniel, M. L. T. Kainuma, J.-F. Lamarque, K. Matsumoto, S. A. Montzka, S. C. B. Raper, K. Riahi, A. M. Thomson, G. J. M. Velders and D. van Vuuren (2011). "The RCP Greenhouse Gas Concentrations and their Extension from 1765 to 2300." Climatic Change (Special Issue), DOI: 10.1007/s10584-011-0156-z

CO2EQ - (For Information only, not CMIP5 recommendation) CO2 equivalence concentrations using CO2 radiative forcing relationship Q = 3.71/ln(2)*ln(C/278), aggregating all (efficacy-adjusted) anthropogenic forcings, including greenhouse gases listed below (i.e. columns 3,4,5 and 8-35), and aerosols, trop. ozone etc. (not listed below).

Lamarque, J.-F., G. P. Kyle, M. Meinshausen. K. Riahi, S. J. Smith, D. P. van Vuuren, A. Conley, F. Vitt. Global and regional evolution of short-lived radiatively-active gases and aerosols in the Representative Concentration Pathways. Climatic Change, doi:10.1007/s10584-011-0155-0, 2011.

From Lamarque et al. 2011. All RCPs have similar emission and concentration trajectories for ozone depleting substances (except N20) so all else being equal they should have the same stratospheric ozone trajectory but chemistry-climate coupling changes the distribution of ozone but ozone recovery/increases are larger in RCP8.5 and even exceed 1850 values!36CESM-CAM5 RCP8.5 Warming

Surface Temperature avg(2080-2099)-avg(2006-2025)Variable2006-20252080-2099(2080-2099)-(2006-2025)TS 291.579 288.152 3.426

37RCP8.5 Zonal Mean Surface Warming

How do Southern Ocean cloud feedbacks affect the climate response to increased greenhouse gas forcing?30-50 South weak warming. 60-70ish South seasonality in the warming due to sea ice loss.38