forcing bam with hadisst1.1 for the period 1948-2002 s. grainger, c.s. frederiksen and j.m. sisson...
TRANSCRIPT
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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)
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Contents
• Overview of BAM
• General results
• South-West Western Australia
• Interannual variability over Australia
• Conclusions
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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
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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
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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
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MSLP DJF Climatology (1950 – 2002)
NCEP
C20C (6)
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C20C MSLP DJF Standard Deviation (hPa)
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C20C MSLP DJF External Variability Ratio
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DJF
JJA
Correlation (C20C Z500, Nino3 SST)
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• 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)
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Australia
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Rottnest Island early winter (May-July) rainfall
IOCI (2002)
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Correlations
C20C – NCEP = 0.228
C20C – obs. = -0.239
NCEP – obs. = 0.223
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MSLP JJA Difference (1975-1999) – (1950-1974)
NCEP
C20C (6)
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U200 JJA Climatology
NCEP
1950 - 1974 1975 - 1999
C20C (6)
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U200 JJA Difference (1975-1999) – (1950-1974)
NCEP
C20C (6)
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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
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Australian Surface Air Temperature Variability - DJF
Nce
p
Total Intraseasonal Slow-Predictable
BA
M3
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Australian Surface Air Temperature Variability - DJF
External Slow-Predictable Internal Slow-Predictable
BAM3 Slow-Predictable
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Australian Surface Air Temperature Variability - DJF
Correlations BAM3 vs NCEP
Total vs Total External vs Total External vs Slow-Predictable
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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