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Modeling of Stratospheric Ozone in the Climate System Steven Pawson GMAO, NASA GSFC Judith Perlwitz CIRES, CU/NOAA ESRL Richard S. Stolarski Atmospheric.

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Presentation on theme: "Modeling of Stratospheric Ozone in the Climate System Steven Pawson GMAO, NASA GSFC Judith Perlwitz CIRES, CU/NOAA ESRL Richard S. Stolarski Atmospheric."— Presentation transcript:

1 Modeling of Stratospheric Ozone in the Climate System Steven Pawson GMAO, NASA GSFC Judith Perlwitz CIRES, CU/NOAA ESRL Richard S. Stolarski Atmospheric Chemistry & Dynamics Branch, NASA GSFC Yung Group Caltech Lunchtime Seminar: March 18, 2008

2 Motivation Can be tested with experiments using “chemistry-climate models” (CCMs) that couple chemistry with the circulation Degree of feedback needed for understanding of ozone and climate Impacts formulation of models used in IPCC climate assessments How does climate change impact ozone? How does ozone change impact climate?

3 Greenhouse Gas Scenarios IPCC Fourth Assessment Report, 2007

4 Ozone-Depleting Substances WMO-UNEP Scientific Assessment of Ozone Depletion, 2006

5 Outline of Presentation 1.Brief Description of GEOS CCM 2.Stratospheric Ozone and Temperature: 1960-2005 3.Sensitivity to Sea-Surface Temperature: Past 4.Ozone Change in the 21st Century (C21) 5.Ozone Impacts on the Southern Hemisphere Climate 6.Summary Application of the GEOS CCM to some questions involving ozone and climate (Goddard Earth Observing System Chemistry-Climate Model)

6 1. Brief Description of GEOS CCM A short overview of the model structure and the experiments performed

7 GEOS CCM, Version 1 GEOS-4 General Circulation Model: Flux-form quasi-Lagrangian transport with material vertical coordinate (Lin, 2004) Gravity wave drag after Garcia and Solomon (1984) Sub-grid physics from NCAR CCM3 (Kiehl et al., 1998) Goddard stratospheric chemistry model 35 transported trace species Family approach after Douglass and Kawa (1999) Reaction rates and cross sections from JPL evaluation 14 Resolution (flexible) 2.5°×2° (longitude by latitude) 55 layers, with Δ z ≃ 1-1.5km in stratosphere

8 GCM-Chemistry Coupling Solar radiation:  18 spectral bands covering the range 240nm – 450 µm  heating by O 3, H 2 O, O 2, and CO 2 and cloud effects Longwave radiation:  Six-band model  treats CO 2, H 2 O, O 3, CH 4, N 2 O, CFC11, CFC12 Gas distributions:  Water: from moist physics in troposphere and modified by chemistry (methane oxidation) in stratosphere  CO 2, other GHGs & CFCs: specify surface concentrations from observations or future projected scenarios  Ozone: predicted by model in stratosphere and relaxed to zonal-mean climatology (Logan) in troposphere

9 Model Experiments NameSST/ice GHG (SRES) CFCs (WMO) Span P1HadISSTObs. 1950-2005 P2HadISSTObs.Obs1950-2005 P-Cl1960HadISST Obs (1960 Cl) 19601950-2005 C21-CSSTCCSM3A1bAb2000-2099 C21-HSSTHadGEM1A1bAb2000-2099 C21-CSSTaCCSM2A1bAb1970-2050 C21-HSSTaHadGEM1A1bAb1970-2050 C21-Cl1960CCSM3 A1b (1960 Cl) 19602000-2099 Observed Modeled Past 21st Century

10 2. Stratospheric Ozone and Temperature: 1960- 2005 How did the atmosphere change in the recent past? S. Pawson, R.S. Stolarski, A.R. Douglass, P.A. Newman, J.E. Nielsen, S.M. Frith, and M. Gupta (2008): Goddard Earth Observing System Chemistry- Climate Model Simulations of Stratospheric Temperature-Ozone Coupling between 1950 and 2005. J. Geophys. Res., in press

11 1980-2000 Ozone Change

12 1980-2000 Temp. Change

13 Antarctic Ozone and Temp: Past Ozone Temperature Value in 2000Change from 1980 90  S-60  S means Ozone and temperature changes (1980-2000) in the GEOS CCM Observed SST (HadISST) IPCC GHG changes WMO/UNEP CFC emissions Green - P-Cl1960 Red/blue - P1 and P2 Purple - time slice runs

14 2. Stratospheric Ozone and Temperature: 1960- 2005 - SUMMARY How did the atmosphere change in the recent past? Global ozone loss consistent with that detected in real atmosphere Cooling of stratosphere - about half from ozone loss Antarctic ozone hole leads to substantial temperature change

15 3. Sensitivity to Sea-Surface Temperature: Past How different is the atmosphere when modeled SSTs are used in place of observations?

16 SST: 1985-1994 Observed (HadISST) Simulated (HadGEM1) minus Observed (HadISST) Simulated (CCSM2) minus Observed (HadISST)

17 Pacific SST

18 Tropical 100-hPa Temp. (Jan) P1 and P2 (Natural Variability) C21-HSSTb and P1 (Impacts of cold SST) C21-CSSTb and P1 (Impacts of better SST)

19 Tropical vertical velocity

20 Age of Air

21 Impacts on tropical ozone

22 Impacts on total ozone (Jan)

23 3. Sensitivity to Sea-Surface Temperature: Past How different is the atmosphere when modeled SSTs are used in place of observations? - SUMMARY Cold-biased SST leads to cold biased tropical upper troposphere (less diabatic heating) Cold biased SST leads to decrease in tropical upwelling, with: Increase in mean age of air (global) More ozone in the tropical lower stratosphere

24 4. Ozone Change in the 21st Century (C21) What factors determine ozone change in the future?

25 Total Ozone in Jan & Oct

26 Pacific SST

27 Mean Age of Air

28 Antarctic Ozone: 1960-2100 Total ozone over Antarctica in October in six runs of the GEOS CCM, subject to CFC scenario Ab & IPCC GHG scenario A1b

29 Tropical Ozone: 1960-2100

30 4. Ozone Change in the 21st Century (C21) What factors determine ozone change in the future? - SUMMARY Tropical mean age and ozone show similar responses to lower SST (more ozone and older air) Differences are large in the middle 21st Century but decrease near 2100 as SST differences converge Antarctic ozone is dominated by CFC loading and interannual variability

31 5. Ozone Impacts on the Southern Hemisphere Climate How does stratospheric ozone change impact the tropospheric circulation around Antarctica? J. Perlwitz, S. Pawson, R. Fogt, J.E. Nielsen, W. Neff, The Impact of Stratospheric Ozone Hole Recovery on Antarctic Climate Change. Geophys. Res. Lett., in press

32 Ozone-Antarctic Climate: Past Changes,1969-1999 With Ozone Change No Ozone Change Change in surface pressure in DJF Ozone hole causes substantial seasonal circulation changes, in accord with prior observation- and model-based studies

33 Antarctic O 3 & T in GEOS CCM ∆O 3 ∆T 1999 - 19692094 - 2006 No Cl change

34 O 3 & Climate: GEOS CCM ∆u ∆(SAM) 1999 - 19692094 - 2006

35 DJF Surface Pressure Changes With Chlorine change 1999 - 1969 2094 - 2006 Without Chlorine change

36 Comparison: AR4 C21 Models GEOS CCM, fixed Cl GEOS CCM AR4 models, with no ozone recovery AR4 models, with ozone recovery

37 5. Ozone Impacts on the Southern Hemisphere Climate How does stratospheric ozone change impact the tropospheric circulation around Antarctica? - SUMMARY Strong seasonal anomaly in SH circulation that peaks when ozone hole is strongest Springtime ozone loss leads to strong positive SAM anomaly (stronger westerly winds) in summertime GHG change causes a similar year-round response that increases through 21st Century Ozone impact decreases through 21st Century

38 Summary GEOS CCM shows expected stratospheric response to CFC and GHG loadings Temperature response to ozone change is on the low end of simulated responses SST biases have a strong, direct impact on upwelling in the tropical low stratosphere and ozone Stratospheric ozone change in the C21 is dominated by SST change (GHG) in the Tropics and by interannual variability at high latitudes Seasonal changes in Antarctic circulation are dominated by the summertime response to the ozone hole


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