Simulating UTLS changes in Simulating UTLS changes in chemistry-climate models chemistry-climate models

Andrew Gettelman, NCAR + Andrew Gettelman, NCAR + CCMVal-2 Model PIsCCMVal-2 Model PIs

CCMVal Model PI’sCCMVal = Chemistry Climate Model Validation projectMODEL NAME INSTITUTION PRINCIPAL INVESTIGATORSAMTRAC3 GFDL, USA John AustinCAM3.5 NCAR, USA Jean-Francois LamarqueCCSRNIES NIES, Tokyo, Japan Hideharu AkiyoshiCMAM MSC, U. Toronto, York U., Canada David Plummer, John Scinocca, Ted ShepherdCNRM-ACM Meteo-France, France Martine Michou, Francoise Cheroux, Hubert

TeyssedreE39CA DLR, Germany Martin Dameris, Hella GarnyEMAC MPI Mainz, Germany Andreas Baumgaertner, Christoph Brühl, Patrick

JückelGEOSCCM NASA/GSFC, USA Steven Pawson, Rich Stolarski, Stacey FrithLMDZrepro IPSL, France Slimane BekkiMRI MRI, Japan Kiyotaka ShibataNIWA-SOCOL NIWA, NZ Dan Smale SOCOL PMOD/WRC and ETHZ, Switzerland Eugene Rozanov, Tom PeterULAQ University of L'Aquila, Italy Eva Mancini, Gianni PitariUMETRAC NIWA, NZ Olaf MorgensternUMSLIMCAT University of Leeds, UK Martyn Chipperfield, Sandip Dhomse UMUKCA-METO MetOffice, UK Neal Butchart, Steven Hardiman UMUKCA-UCAM University of Cambridge, UK Peter Braesicke, Olaf Morgenstern, John PyleWACCM (v.3) NCAR, USA Rolando Garcia, Andrew Gettelman, Doug Kinnison

Tropical Circulations ‘appear’ to be Changing

Seidel et al, Nature Geoscience 2008

Implications• Profound effects on UTLS• Impacts on Precipitation, Regional Climate• Is the UTLS diagnostic or does it affect the

response? (is there a feedback in the UTLS)

Theories/Mechanisms• Jets strengthen due to radiative forcing

– Thermal Wind Balance in UTLS (e.g.: 200hPa)– Ozone depletion makes hemispheres asymmetric

• Stronger jets alter stability & wave propagation– Changes baroclinic instability

Frierson et al 2007, Held & Hou 1980, Held 2000– Increase in Phase speed pole-ward breaking displacement

(Chen & Held 2007)• Surface forcing (mean temp or ∂T/∂y)

• Due to changes in mean T mostly; similar effect• Also changes baroclinic instability

• Note: change in static stability (Δθ) caused by moisture too, not just ΔT

• Differences: Local (UTLS) or Tropical Forcing?

Simulation Results from CCMVal-2• Models in support of WMO-2010• Partial results from 17 models, 4 re-analyses• REF-B1: 1960-2005 Historical Runs

– Observed SST, GHG, Halogens, Volcanoes

• REF-B2: 1960-2100– IPCC A1B GHGs beyond 2005, WMO Halogens– Simulated (CMIP GCM) SSTs, or Coupled Ocean

• This work: Preliminary Results – Can we see these features?– Mechanisms?

Diagnostic Description

Diagnostics:1. Tropopause Pressure trends2. Width between LRT3. Jet Speed4. Width between Jets5. Meridional Streamfunction6. OLR7. Precipitation

X X

Tropopause PressureAnnual Zonal Mean Trend (hPa/yr)

Correlation with Observations

Trends in Subtropics are significantSH Larger Trends (1-2odecade-1) than NH

Variability Dominated by Volcanic effects

Tropopause Width at 200hPa

• Width Generally Increasing• Not statistically significant

– large variability

• Anomalies not strongly correlated– Re-analysis anomalies also

• Note Drop after 2000– Trends not monotonic?

Full Field

Anomalies

Jet Maximum Speed at 200hPaSimulated Anomalies correlated with analyses

AN

OM

ALI

ES

FU

LL S

PE

ED

SH NH

Jet Width at 200hPa

• Mixed trends, not significant– Dominated by variability (ENSO)

• Simulated variability correlated with Re-analyses

• Note:– Coarse resolution (on model grid)– not interpolated– No Smoothing

Full Field

Anomalies

Summary: 1960-2005 • Coarse resolution (200-500km) limiting

– Easier for ‘interpolated’ diagnostics

• Changes often are less than variability– Trends often not significant – Differ between Re-analyses

• Can see the forcing (ENSO, Volcanoes) in Variability• Simulated variability correlated with Re-analyses

– Inter-annual variations (also looking at seasonal)– Diagnostics: Jet Speed & Width, Tropopause Pressure– Tropopause width not as well correlated

Future Scenarios• Extra-tropical (Polar) Tropopause Height

– Discussed by Michaela on MondayS. Hemisphere N. Hemisphere

Trends in SH are visibly not monotonic

Effects of O3 Depletion on Trends

• SH Tropopause Trends are affected by O3 depletion

• Trends largest with O3 depletion (1960-2000)

• Lower trends with O3 recovery (2000-2050)

• Climate change (GHGs) during all periods

• N. Hemisphere trends more monotonic

• Overall trend is similar between hemispheres

1960-2000

2001-2050

2051-2099

Tropopause Width Changes at 200hPa

• Overall trends fairly consistent across models: +0.5o decade-1

Jet Max Speed increases at 200hPa

• Jet Maximum Speed increases in both hemispheres

• Differences in simulated trends (0.2-0.3m s-1 decade-1)

• Not clear if SH trends are monotonic (need to do some further statistical analysis)

N. Hemisphere

S. Hemisphere

Conclusions (so far)• Models ‘consistent’ with assimilated systems

– Variability is good (necessary but not sufficient)– If mechanisms are resolved scale waves & get variability, then

perhaps get trends

• Future trends in tropopause height affected by O3

– Does this translate into changes in circulation/climate?

• Jet speed increases in future, tropopause widens– Quantitatively consistent with other work– Meridional Streamfunction zero latitude moves poleward– Broadly matches theories

Next Steps:– Precipitation changes?– Pick apart effects in simplified models: Role of UTLS

O3 Prediction in LMS|40-60| Lat, 200-100hPa

S. Hemisphere N. Hemisphere

SH: O3 loss, recovery, ‘super recovery’NH: ‘Flat’ in 20th Century, 20% increase in 21st Century

Note: Upper (150-100hPa) & Lower (250-150) LMS similar

Also: Historical runs and comparison to NIWA-O3 data set

Ozone Trends (%) 1960-2100

CCMVal Model Ensemble (Credit: Birner)

Plug: Community Diagnostics

• Plots built with a CCMVal-diagnostic package• Easy to do complex analysis with models

– O3 plots done this morning

• Bring observations to models• Interested? Talk to me.