1. Forcing BAM With HADISST1.1 for the Period 1948-2002 S. Grainger, C.S. Frederiksen and J.M. Sisson Bureau of Meteorology Research Centre, Melbourne, Australia Acknowledgements: Z. Sun (BMRC), B. McAvaney (BMRC), X. Zheng (NIWA)

2. Contents Overview of BAM General results South-West Western Australia Interannual variability over Australia Conclusions

3. BAM Climate Model T47L17 Spectral Model (  = 0.991 to 0.0089) Sun – Edwards – Slingo radiation scheme (allows for aerosols) Prognostic clouds (CSIRO – Rotstayn) Mass-flux convection CHASM Land Surface Scheme

4. C20C Forcings HADISST 1.1 SST and sea-ice distribution –Sea-ice is on/off in BAM CO 2 from lookup table SPARC ozone trend after 1975 Stratospheric volcanic aerosol time series Tropospheric aerosol climatology (GADS) Time-varying solar orbital parameters –Solar Constant is fixed Initialised at 0Z 1 January 1948 –IC 0Z 1-10 January 1988 from AMIP run

5. Status Experiment 2 –9.8 ensemble members completed –Presenting results from SIX (6) members –Time series and standard diagnostics to be placed on Bureau DODS server “soon” Experiment 0 –To be started 2 nd Quarter 2004 Experiment 1 –Not yet started

8. MSLP DJF Climatology (1950 – 2002) NCEP C20C (6)

9. C20C MSLP DJF Standard Deviation (hPa)

10. C20C MSLP DJF External Variability Ratio

11. DJF JJA Correlation (C20C Z500, Nino3 SST)

12. Sudden decrease in early winter (MJJ) rainfall in late 1960’s –Affects Perth water supply, land-use and the environment Appears to be caused by changes in large- scale weather patterns –Changes can be seen in, eg, NCEP reanalysis –Is it anthropogenic? South-West Western Australia (SWWA)

13. Australia

14. Rottnest Island early winter (May-July) rainfall IOCI (2002)

15. Correlations C20C – NCEP = 0.228 C20C – obs. = -0.239 NCEP – obs. = 0.223

16. MSLP JJA Difference (1975-1999) – (1950-1974) NCEP C20C (6)

17. U200 JJA Climatology NCEP 1950 - 19741975 - 1999 C20C (6)

18. U200 JJA Difference (1975-1999) – (1950-1974) NCEP C20C (6)

19. Interannual variability over Australia Use technique of Zheng et al. (J. Clim. 2000) –More details in Carsten Frederiksen’s presentation on Tuesday Monthly means for each month in season Generate intraseasonal, and slow internal and external interannual variability contributions

20. Australian Surface Air Temperature Variability - DJF Ncep TotalIntraseasonalSlow-Predictable BAM3

21. Australian Surface Air Temperature Variability - DJF External Slow-PredictableInternal Slow-Predictable BAM3 Slow-Predictable

22. Australian Surface Air Temperature Variability - DJF Correlations BAM3 vs NCEP Total vs TotalExternal vs TotalExternal vs Slow-Predictable

23. Conclusions BAM reproduces many aspects of the climate of the 20 th Century –Responds well to SST forcing –Is able to capture many aspects of interannual variability BAM does less well at reproducing climate changes –There is little apparent response to changes in radiative forcings