The Madden-Julian Oscillation simulated by the Beijing Climate Center’s AGCM

1. 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

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

3. 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)

4. 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

5. 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)

6. Comparison of time-space spectrum of U850

7. Comparison of time-space spectrum of precipitation

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

9. 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

10. Comparison: variance of U850 MJO；ECMWF

11. Variance of U850 MJO；NCEP

12. variance of U850 MJO；BCC2

13. Comparison:variance of U850 MJO;CAM3

14. Annual cycle of MJO for U850 ；ECMWF

15. Annual cycle of MJO for U850 ;NCEP

16. Annual cycle of MJO for U850 ;BCC2

17. Annual cycle of MJO for U850 ；CAM3

18. The propagating speed of MJO for U850；ECMWF & NCEP

19. The propagating speed of MJO for U850；models

20. 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

21. 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

22. 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.

23. Thanks！