Freie Universität Berlin

Temperature and circulation changes in the stratosphere

- Summary of previous workand outlook -

Ulrike Langematz

Freie Universität Berlin

How much of the observed stratospheric thermal and dynamical changes can be attributed to

stratospheric ozone changes?

Freie Universität Berlin

Models for ozone change studies

GCMs: Atmospheric General Circulation Models, integrated with prescribed ozone perturbations

• from observations (Langematz, 2000; Rosier and Shine, 2000; Ramaswamy and Schwarzkopf, 2003; Langematz et al., 2003)

• from offline-CTM calculations (Posters of Stolarski et al.; Schwarzkopf et al.)

GCMs with parametrized chemistry (calculated ozone change) (Rind et al., 1998; Shindell et al., 2001)

CCMs: Chemistry Climate Models with interactive chemistry modules (calculated ozone change)

(Austin, 2002; Manzini et al., 2003)

Freie Universität Berlin

GCM Ozone perturbations studies

Experimental design

20 year time slice experiments with modified O3 and CO2 in FUB-CMAM

„Change“ ≙ statistical, mean difference 2000 minus 1980

Freie Universität BerlinFreie Universität Berlin

(WMO, 1998)

Observed O3 trends 1979-1997

Ozone perturbations: Observed trends 1980-2000Constructed O3 trends for GCM

(Langematz, 2000)

annual mean

Two zonal mean ozone trend datasets available:

• Randel and Wu, 2000 • Langematz, 2000

Freie Universität Berlin

• Rosier and Shine, 2000• Langematz, 2000, Langematz et al., 2003• Ramaswamy and Schwarzkopf, 2003 Schwarzkopf and Ramaswamy, 2003

Shine et al., 2003

MA-GCM studies of the period 1980-2000 with prescribed ozone profile changes:

GCM Ozone perturbations studies I

Freie Universität Berlin

Annual and global mean temperature change due to observed O3 trend

Previous studies

Freie Universität Berlin

Shine et al., 2003

Models using Height-Resolved Observed Ozone Trends Dataset

– 1.25 to – 2.3 K/dec

– 0.25 to – 0.45 K/dec

Freie Universität BerlinFreie Universität Berlin

Shine et al., 2003

Models using Height-Resolved Observed Ozone Trends Dataset

Annual mean temperature change at 50 hPa

Previous studies

?

Freie Universität Berlin

Previous studies

GCM integrations with prescribed ozone changes

• do not reproduce the observed upper stratosphere cooling.

• do reproduce the weak middle atmosphere cooling.

• do not reproduce the lower stratosphere global mean cooling.

• do not reproduce the lower stratosphere mid-latitude cooling.

Main results

Missing processes? GHG? H2O?

Missing feedback? CCMs?

Freie Universität Berlin

Previous studies

Lower/middle stratosphere

Annual and global mean temperature change

Shine et al., 2003

Coupled chemistry models

Freie Universität Berlin

2 Goals:

Model assessment Model improvement

If model agreement Climate change assessment

GRIPS Task 3c

Coordinated GCM experiments of the period 1980-2000 with

prescribed observed ozone changes

GRIPS: GCM Realitiy Intercomparison Project for SPARC (Coordinators: Steven Pawson and Kunihiko Kodera)

Extension of Shine et al., 2003, with focus on dynamics

Freie Universität Berlin

The GRIPS 3c task

Perform two 20 year equilibrium GCM integrations• 1980 control-run • 2000 „ozone change“ run

Only difference between runs: prescribed ozone distribution for radiation code

• 1980: 1980 ozone climatology (zonal & monthly mean)• 2000: 1980 ozone climatology +observed trends 1980-2000

Ozone climatology and trends available from• Langematz (2000) • Randel and Wu (2000)

Freie Universität BerlinFreie Universität Berlin

GRIPS Task 3c

New models

CCSR/NIES AGCM • Version 5.7b • T42 L55 (0-83 km)

• O3: climatology and trends: L(2000)

WACCM • NCAR CCM3 + TIME-GCM (Sassi et al. 2002) • T63 L66 (0-140 km)

• O3: climatology and trends: R&W (2000)

Kyushu University GCM • T21L37 (0-83 km) (Miyahara et al., 1995) • O3: climatology and trends: L(2000)

MRI/JMA98 Model • T42 L45 (0-83 km) (Shibata et al., 1999) • O3: AMIP climatology, R&W (2000) trends

New in 2005:

NASA-GSFC: 2 sets of model experiments using R&W and L- ozone trendsUM model

Freie Universität BerlinFreie Universität Berlin

Annual and global mean temperature change(K/decade)

GRIPS Task 3c

WACCMNIESMRIKUFUB

altit

ude

[km

]

Freie Universität Berlin

WACCMNIESMRIKUFUB

Freie Universität Berlin

Annual and global mean temperature change(K/decade)

GRIPS Task 3c

–0.9 to –1.5 K/dec

– 0.25 to – 0.48 K/dec

altit

ude

[km

]

Freie Universität BerlinFreie Universität Berlin

Annual mean temperature change (K/decade)

SSU-satellite data, 1979-97

Scaife et al., 2000

FUB

KU NIES

WACCM MRI

GRIPS Task 3c

Freie Universität Berlin

NH summer (JJA) change, 30°N

GRIPS Task 3c

WACCMNIESMRIKUFUB

SW heating rate change [K/d/dec]Temperature [K/dec]

L-O3R&W-O3

Ozone change [%/decade]

To do: temperature change per ozone change, in progress

Freie Universität Berlin

Lower stratosphere temperature change in NH mid-latitudesK/decade

Freie Universität Berlin

FUB-analyses 1979-2000

• Models do not show uniform response. Model deficit? • No model is able to reproduce mid-latitude temperature decrease. No ozone effect!

FUB

KU NIES

WACCM MRI

GRIPS Task 3c

Freie Universität BerlinFreie Universität Berlin

NCEP-data: 1979-2000

Lower stratosphere temperature change at high latitudes(K/decade)

FUB

KU

WACCM

NIES

MRI

• Models show different cooling due to SH spring ozone depletion. Radiation code? Ozone?• No model reproduces observed NH polar spring cooling. No ozone effect.

GRIPS Task 3c

Freie Universität BerlinFreie Universität Berlin

Temperature change in DJF(K/decade)

FUB

NIESKU

WACCM MRI

GRIPS Task 3c

Freie Universität Berlin

DJF change in zonal wind, wave forcing, and residual circulation, 1980-2000

Orange (yellow): 99% (95%) stat. significance.

v* [m/s/decade]

w* [mm/s/decade]D [m/s/day/decade]

u [m/s/decade]

latitude

latitudeweaker residual circulation

stronger polarnight jet

weaker wave driving

Langematz et al., 2003

FUB-CMAM (with prescribed O3 change)

Stratospheric ozone change causes dynamical changes.

Freie Universität Berlin

Change in wave forcing in NH winter (DJF)[m/s/day/decade]

GRIPS Task 3c

FUB

KU

MRI

Freie Universität Berlin

Change in residual vertical velocity in NH winter (DJF)[mm/s/decade]

GRIPS Task 3c

FUB KU

MRI NI

Freie Universität BerlinFreie Universität Berlin

Zonal wind change in DJF(m/s/decade)

FUB

KU NIES

WACCM MRI

GRIPS Task 3c

Models do not show a consistent dynamical response.

Freie Universität BerlinFreie Universität Berlin

Change in polar vortex strength in NH spring (dam/decade)

NIES

MRI

GRIPS Task 3c

Trend 1979-2000

90‘s-70‘s(1991-2000)-(1971-1980)

FUB-data

FUB-data

FUB

March

Freie Universität Berlin

Equilibrium vs. transient response in WACCMTemperature, annual mean, [K/decade]

100hPaequilibrium

transient 100hPa

GRIPS Task 3c

Freie Universität Berlin

Summary

GCM ozone perturbation experiments:

- show global stratospheric cooling due to ozone depletion

- do not explain polar lower stratosphere cooling in NH spring

- do not explain mid-latitude cooling in lower stratosphere

No uniform dynamical signal

Work in progress

Freie Universität Berlin

More work planned in 2005

Assessment of trends in the tropical UTLS

(part of EU-SCOUT-O3 project)

Includes

trends from observations

trends from CCM simulations (with SPARC-CCMval activity)

To validate past CCM runs and coming runs with new scenarios

Work is in progress at FUB