ROMI is computed using OLR only and as such is a purely convective index of the MJO. The EOFs depend on the day of year, latitude and longitude. To plot the diagram in the same phase space as the Wheeler-Hendon RMM index, the sign of ROMI PC1 is reversed and the PC ordering is switched, so that ROMI(PC2) is analogous to RMM(PC1) and -ROMI(PC1) is analogous to RMM(PC2).

The RMM is provided by the Bureau of Meteorology Australia. RMM is computed using interpolated OLR from PSL and 850hPa and 200hPa zonal winds from the NCEP reanalysis. The EOFs only depend on longitude.

The VPM index was computed using zonal wind and velocity potential based on the CORe Reanalysis. The VPM PC signs were adjusted to match the RMM index signs for the phase plot. Note that this index is different than the original VPM based on the NCEP/NCAR Reanalysis Version 1.