Results > CMIP mean state and variability > MJO
MaddenJulian Oscillation (MJO)
The MJO consists of largescale regions of enhanced and suppressed convection, and associated circulation anomalies in the tropics that propagate eastward, mainly over the eastern hemisphere, with a time scale of ~3060 days (Madden and Julian 1971, 1972, 1994). Its largescale nature and period are easily seen via frequencywavenumber decomposition of nearequatorial data (10°S to 10°N), which partitions the raw anomalies into eastward and westward propagating components and also as a function of frequency (cycles/day). The frequencywavenumber decomposition technique has been widely used to assess if models properly represent this basic characteristic of the MJO (e.g., CLIVAR MJO Working Group 2009; Kim et al. 2009; Ahn et al. 2017).
Here we apply the frequencywavenumber decomposition method to precipitation from observations (GPCPbased; 19972010) and the CMIP5 and CMIP6 Historical simulations for 19852004. For disturbances with wavenumbers 13 and frequencies corresponding to 3060 days it is clear in observations that the eastward propagating signal dominates over its westward propagating counterpart. Thus, an important metric is the eastward/westward power ratio (EWR) for the abovementioned wavenumbers and frequencies, which is about 2.5 in observations.
The EWR results are based on the work of Ahn et al. (2017). Implementation of these and other MJO analysis into the PMP is part of a PCMDI collaboration with Prof. Daehyun Kim (University of Washington), his group, and the WGNE MJO Task Force.
Summary statistics in Interactive Bar Charts
General Results

Preliminary findings: The Interactive Bar Chart provides a comparison of the EWR among the observations, CMIP5, and CMIP6. As presented, this plot facilitates comparison of the EWR by CMIP5 and CMIP6 groups, by modelling center, and by the ascending order of the value.

Cautionary Note: The MJO frequency and wavenumber windowing is based on observations. Thus, while the EWR provides an initial evaluation of the propagation characteristics of the observed and simulated MJO, it is instructive to look at the frequencywavenumber spectra, as in some cases the dominant periodicity in a model may be different than in observations. Figures of the frequencywavenumber power spectra are obtained by leftclicking on the statistics that popup when you hover your mouse over a histogram bar (mean over all realizations) or a dot (for an individual realization).
References
Ahn, M.S., D. Kim, K. R. Sperber, I.S. Kang, E. Maloney, D. Waliser, H. Hendon, 2017: MJO simulation in CMIP5 climate models: MJO skill metrics and processoriented diagnosis. Clim. Dynam., 49, 40234045. doi: 10.1007/s0038201735584.
CLIVAR MaddenJulian Oscillation Working Group (Waliser, D., K. Sperber, H. Hendon, D. Kim, E. Maloney, M. Wheeler, K. Weickmann,, C. Zhang, L. Donner, J. Gottschalck, W. Higgins, I.S. Kang, D. Legler, M. Moncrieff, S. Schubert, W. Stern, F. Vitart, B. Wang, W. Wang, and S. Woolnough), 2009: MJO simulation diagnostics. J. Clim., 22, 30063029. doi: 10.1175/2008JCLI2731.1.
Kim, D., K. R. Sperber, W. S. Stern, D. Waliser, I.S. Kang, E. Maloney, W. Wang, K. Weickmann, J. Benedict, M. Khairoutdinov, M.I. Lee, R. Neale, M. Suarez, K. ThayerCalder, and G. Zhang, 2009: Application of MJO simulation diagnostics to climate models. J. Clim., 22, 64136436. doi: 10.1175/2009JCLI3063.1.
Madden, R. A., and P. R. Julian, 1971: Detection of a 40–50 day oscillation in the zonal wind in the tropical Pacific. J. Atmos. Sci., 28, 702–708. doi: 10.1175/15200469(1971)028<0702:DOADOI>2.0.CO;2
Madden, R. A., and P. R. Julian, 1972: Description of globalscale circulation cells in the tropics with a 40–50 day period. J. Atmos. Sci., 29, 1109–1123. doi: 10.1175/15200469(1972)029<1109:DOGSCC>2.0.CO;2
Madden, R. A., and P. R. Julian, 1994: Observations of the 40–50day tropical oscillation—A review. Mon. Wea. Rev., 122, 814–837. doi: 10.1175/15200493(1994)122<0814:OOTDTO>2.0.CO;2