The Madden-Julian Oscillation simulated by the Beijing Climate Center

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The Madden-Julian Oscillation simulated by the
Beijing Climate Centers 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 Ps
• 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)
• VariablesU 850 hPa Precipitation

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The spectral structure

• The U850 and PP for each year (365 days) at each
  latitude are used to do time-space spectral
  analysis by FFT
• Averaged over 10S-10N
• Averaged 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 MJOECMWF
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Variance of U850 MJONCEP
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variance of U850 MJOBCC2
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Comparisonvariance of U850 MJOCAM3
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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 U850ECMWF
NCEP
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The propagating speed of MJO for U850models
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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!