Beijing Climate Center, China Meteorological Administration 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

Contents Introduction Model and data Results spectral structure 　　　MJO variance distribution 　　　Annual cycle of the MJO (Wavelet analysis) 　　　Propagating speed Discussion

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)

Model run and validation data 　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

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)

Comparison of time-space spectrum of U850

Comparison of time-space spectrum of precipitation

Comparison of time-space spectrum of precipitation (pentad data)

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

Comparison: variance of U850 MJO；ECMWF

Variance of U850 MJO；NCEP

variance of U850 MJO；BCC2

Comparison:variance of U850 MJO;CAM3

Annual cycle of MJO for U850 ；ECMWF

Annual cycle of MJO for U850 ;NCEP

Annual cycle of MJO for U850 ;BCC2

Annual cycle of MJO for U850 ；CAM3

The propagating speed of MJO for U850； ECMWF & NCEP

The propagating speed of MJO for U850；models

Discussions It can reproduce the MJO variance space distribution 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

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

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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