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

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

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)

　

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 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.

Thanks！