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Forcing BAM With HADISST1.1 for the Period 1948-2002

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). Contents. Overview of BAM General results

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Forcing BAM With HADISST1.1 for the Period 1948-2002

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  1. Forcing BAM With HADISST1.1 for the Period 1948-2002 S. Grainger, C.S. Frederiksen and J.M. SissonBureau 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 • CO2 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 2nd Quarter 2004 • Experiment 1 • Not yet started

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

  7. C20C MSLP DJF Standard Deviation (hPa)

  8. C20C MSLP DJF External Variability Ratio

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

  10. South-West Western Australia (SWWA) • 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?

  11. Australia

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

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

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

  15. 1950 - 1974 1975 - 1999 U200 JJA Climatology NCEP C20C (6)

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

  17. 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

  18. Total Intraseasonal Slow-Predictable Ncep BAM3 Australian Surface Air Temperature Variability - DJF

  19. BAM3 Slow-Predictable External Slow-Predictable Internal Slow-Predictable Australian Surface Air Temperature Variability - DJF

  20. Total vs Total External vs Total External vs Slow-Predictable Australian Surface Air Temperature Variability - DJF Correlations BAM3 vs NCEP

  21. Conclusions • BAM reproduces many aspects of the climate of the 20th 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

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