1. Stratospheric Chemical-Climate Variability during the 20th century Andreas Fischer, Stefan Brönnimann, Eugene Rozanov, Nico Zeltner, Stefan Krähenmann CLIVAR Climate of the 20th century workshop, IACETH, 15-03-2007

2. Stratospheric Chemical-Climate Variability during the 20th century Table of Contents Motivation SOCOL Model / Model set-up Boundary Conditions - Land Use Change - Stratospheric Aerosol Data Chemistry Climate Features 1901 - 1909 Conclusion

3. Stratospheric Chemical – Climate Variability Stratosphere subject to a large dynamical variability, including the interannual-to-decadal scale (Solomon, 1999) Volcanic Eruptions, Solar Variability, ENSO, and other parameters affect stratospheric climate and ozone to a large degree (see Robock 2000; Hood 2004; Brönnimann 2007) Stratospheric interannual-to-decadal variability affects climate at the ground and vice versa (Shindell et al., 2001; Baldwin et al., 2001) Therefore interesting to investigate the mechanisms leading to stratospheric climate variability and to understand the processes modulating them.  Chemistry Climate Model as an ideal toolMotivation

4. Climate and Stratospheric Ozone during the 20th century March Monthly mean temperature (30hPa, NP, 1956 – 2004 ) ( Labitzke et al. 2004)

5. Chemistry Climate Modelling (CCM) Most CCM studies focus on the past 25 years (Satellite period), focusing on anthropogenic influences (greenhouse effect and stratospheric ozone depletion) and major volcanic eruptions (El Chichon, Pinatubo) Only a few CCM simulations go back to 1950s (Shindell et al., 1998; Dameris et al., 2004) However, to represent natural variability of the stratosphere, it is essential to cover longer time periods. Low-frequency variability can be related to climate modes, such as AMO, IPO and to solar variability. Also, much larger variations than during the past 50 years occurred earlier (e.g. strong El Niño 1940-42, Brönnimann et al., 2004, or volcanic eruption of Krakatoa)Motivation  Trying to fill this gap by simulating the whole 20th century by means of the CCM SOCOL  9 Ensemble Members with most realistic forcing

6. CCM Solar Climate Ozone Links (SOCOL) General circulation model MA-ECHAM-4 coupled to chemistry-transport model MEZON (Rozanov et al., PMODWRC, Davos) Spectral model with T30 horizontal truncation 39 levels, from surface to 0.01 hPa Time step for dynamics and physics: 15 min; for radiation and chemistry: 2 hours Simulation of 60 chemical species; Reactions: 135 gas-phase, 52 photolysis and 16 heterogeneous reactions on/in sulfate aerosol Coupling between chemistry and GCM by ozone, water vapor, N 2 O, CH 4, CFCs SOCOL can be run on normal PCs SOCOL Model

7. Model Setup Horizontal transport of substances with Semi-Lagrangian Scheme; Vertical transport with Prather Scheme Use of Family Transport Concept for Chlorine, Bromine, and Nitrogen containing species: Transport Cly, Bry, and NOy individually and as family in order to conserve total mass Mass fixer of O3 applied only for latitude band 40°S – 40°N; better agreement with observations and with a accurate transport scheme (Prather- Scheme) Spin up performed with off-line CTM-version for 10-yr long run simulation. Driven by temperature, water vapour, and daily circulation from a previous SOCOL 25yr time-slice simulation (Egorova 2005). 100yr transient simulation started in January 2007. Full output expected by end of August. SOCOL Model

8. Boundary conditions Land surface change Sea Ice GHG / ODS / NOx / CO Solar irradiance Sea surface temperature Stratospheric aerosols SOCOL Tropospheric aerosols Quasi-biennial Oscillation Reconstruction, Brönnimann et al. HadISST, Rayner et al. HYDE database Lean et al. WMO/GISS EDGAR-HYDE GADS climatology GISS data, Sato et al. Stratospheric Chemical-Climate Variability during the 20th century

9. HYDE database Land Use Change Dataset 17001990 - 20 vegetation classes on 0.5° x 0.5° grid - 8 years: 1700 / 1750 / 1800 / 1850 / 1900 / 1950 / 1970 / 1990 Pasture land Crop land

10. Mapping to ECHAM Land Use Change Dataset 1Urban …… 9Upland Tundra …… 96Deciduous Tree Crop Surface Background Albedo Surface Roughness Length Leaf Area Index Vegetation Ratio Forest Coverage Field Capacity ECHAM vegetation classes (Hagemann et al. 2002) HYDE vegetation classes Considered land surface parameters

11. Forest coverage Land Use Change Dataset IGBP dataset at 1 km resolution Original in ECHAM4 HYDE mapped to ECHAM

12. Procedure: Look-up-table …… …… Number densityrmod Surface Area Density scaling factor Interpolation of the extinction to the 8 spectral bands of ECHAM using Mie calculations (look-up- table) T, wts, sigma fixed extinction at 1E-4 GISS data 1850 – 1999 (Sato et al., 1993) Stratospheric Aerosol Dataset Input: - Effective radius as a function of latitude - Optical Depth (@ 550nm) as function of latitude and 4 altitude levels Output: - Surface Area Density, Number Density - Extinction Coefficients, Single Scattering Albedo and Asymmetry Factors for 8 spectral intervals

13. Surface Area Density (1850-1999, global mean, 100hPa) Stratospheric Aerosol Dataset SAGE dataset 1979-2002 GISS dataset 1850-1999 [um 2 /cm 3 ]

14. Sea Level Pressure HadSLP2 (climatology 1901 – 1909) Climate 1901 - 1909 Summer (JAS) Winter (JFM) Spring (AMJ) Autumn (OND) [hPa]

15. Sea Level Pressure SOCOL (climatology 1901 – 1909) Climate 1901 - 1909 Summer (JAS) Winter (JFM) Spring (AMJ) Autumn (OND) [hPa]

16. Total Ozone SOCOL (Zonal Mean, 1901 – 1909) Climate 1901 - 1909

17. 40 and 100 hPa Temp. Anomaly SOCOL (versus climatology 1901–1909) Climatic effects after Santa Maria 1902 JFM 1903 JFM 1904 Temp at 40 hpa Temp at 100 hPa [K]

18. Surface Air Temp. Anomaly SOCOL and Obs. (versus climatology 1901 – 1909) Climatic effects after Santa Maria 1902 JFM 1903 JFM 1904 SOCOL HadCrut [K]

19. 100 hPa GPH Anomaly Reconstructions (versus climatology 1901 – 1909) Climatic effects after Santa Maria 1902 JFM 1903 JFM 1904 SOCOL Reconstructions [m]

20. Conclusion 20th century runs by the CCM SOCOL provides useful insights in causes and processes related to interannual-to-decadal variability. Boundary Conditions have been successfully compiled for the whole century The SOCOL simulation compares reasonably well with HadSLP data for the first decade of the century For the winter month after Santa Maria eruption: the meridional gradient of Temperature at 40 hPa is increased whereas at 100 hPa the gradient of temperature and geopotential height strongly varies with longitude in the SOCOL simulation. Observational Surface Air Temperature show a anomalous warming over Europe and North America in winter 1903, consistent with previous studies about tropical eruptions. SOCOL reproduces some of these features, but magnitudes are often underestimated. In winter 1904 Temperature and Geopotential Height Anomalies are almost reversed compared to one year before in both, simulation and observational datasets. Stratospheric Chemical-Climate Variability during the 20th century

21. Surface Air Temperature Anomaly with respect to climatology 1901 - 1909 Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

22. Surface Air Temperature Anomaly with respect to climatology 1901 - 1909 Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

23. 40hPa Temp. Anomaly SOCOL (versus climatology 1901–1909) and SAD Climatic effects after Santa Maria 1902 JFM 1903 JFM 1904 [K] [um 2 /cm 3 ] Temperature Surface Area Density Latitude Pressure

24. Sea Level Pressure Anomaly SOCOL (with respect to climatology 1901–1909) Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

25. Sea Level Pressure Anomaly HadSLP (versus climatology 1901–1909) Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

26. 100hPa Ozone Anomaly with respect to climatology 1901 - 1909 Climatic effects after Santa Maria 1902 OND 1902 JFM 1903

27. Vegetation Ratio Land Use Change Dataset beforeafter IGBP dataset at 1 km resolution

28. 100hPa Temperature Anomaly SOCOL (versus climatology 1901–1909) Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

29. 100hPa GPH Anomaly SOCOL (versus climatology 1901–1909) Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904

30. 100 hPa GPH Anomaly Reconstructions (versus climatology 1901 – 1909) Climatic effects after Santa Maria 1902 AMJ 1903 OND 1902 JFM 1903 JFM 1904