The Madden-Julian Oscillation simulated by the Beijing Climate Center’s AGCM
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The Madden-Julian Oscillation simulated by the Beijing Climate Center’s AGCM
Dong Min Wu Tongwen Wang Zaizhi Zhang Fang
Beijing Climate Center, China Meteorological Administration
Beijing, 100081 PRC
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Contents Introduction Model and data Results spectral structure MJO variance distribution Annual cycle of the MJO (Wavelet analysis) Propagating speed Discussion
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Model and Data The Beijing Climate Center Model
(BCC_AGCM2.0.1)
It is developed based on NCAR CAM3.0 (released on 2004 09)
A refference Atmosphere is introduced to the model, The prognostic variable T and Ps become T´ and P´s
A new Zhang_Mcfarlane convection scheme (2005) replaced the original one (1995)
Latent heating calculation modified over ocean
Snow cover representation slightly changed NCAR CAM3 (Collins et al. 2004)
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Model run and validation data
Model run
Monthly SST from 1949,9-2001,10 (52 years)
Validation data: NCEP(1948-2002),ECMWF(1957-2002)
CMAP (1979-200) Variables : U 850 hPa; Precipitation
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The spectral structureThe U850 and PP for each year (365
days) at each latitude are used to do time-space spectral analysis by FFT
Averaged over 10S-10NAveraged over 51 year (1950-2000)
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Comparison of time-space spectrum of U850
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Comparison of time-space spectrum of precipitation
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Comparison of time-space spectrum of precipitation (pentad data)
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Variance of MJO
After the spectral Analysis Take the Waves of wave number 1 – 5 and
period 20 -90 days to reconstruct a MJO time series
Plot the variance of the MJO series in the tropics (20S-20N) for each season
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Comparison: variance of U850 MJO ; ECMWF
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Variance of U850 MJO ; NCEP
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variance of U850 MJO ; BCC2
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Comparison:variance of U850 MJO;CAM3
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Annual cycle of MJO for U850 ; ECMWF
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Annual cycle of MJO for U850 ;NCEP
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Annual cycle of MJO for U850 ;BCC2
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Annual cycle of MJO for U850 ; CAM3
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The propagating speed of MJO for U850;ECMWF & NCEP
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The propagating speed of MJO for U850 ; models
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Discussions The BCC AGCM can simulate the MJO prety
well. The ability of BCC model in simulating the
MJO is much improved than CAM3.0 It can reproduce the time-space structure of
the U850 and precipitation In the tropics
It can reproduce the MJO variance space distribution
The simulated annual cycle of MJO is close to the observation.
The convection scheme is a key issue in the simulating the MJO
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The problems need to be solved The simulated MJO is not concentrate on the 30-
60 days. It slightly moved to high frequency The simulated MJO space distribution has some
difference with the observation. The annual cycle of the simulated MJO also has
some difference from the observation, especially, the simulated MJO is too strong in summer.
The simulated MJO has more fast propagating speed than the observation
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Future Work
Analysis the mechanism of how can the convection scheme influence the MJO
The impact of the surface heating flux on the MJO simulation.
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Thanks!