Dataset DOI: 10.5061/dryad.sxksn03dw

Description of the data and file structure

This dataset contains the simulation data, observational data, and scripts for creating the figures in Takasuka et al. (2025). It also provides NCL (NCAR command language) scripts for plotting the figures. 

Files and variables

File: Takasuka_etal_2025_Science.tar.gz

Description: All the data have the netCDF format. Variable information has been provided in the metadata of the files, so we do not repeat the details here. The directory structure is as follows.

— NICAM
This directory stores the three types of data. 

1) Atmospheric data composited for the Nov-1, Dec-1, and Dec-2 regimes. They exist at the directories of [Nov, Dec]/[Nov-1, Dec-1, Dec-2]/[case, com]. The directories of “case” and “com” store the 2d/3d variables for each case and composites categorized into the regimes, respectively. In “case” and “com”, there are some directories with different data contents.

• [none]: default anomalies
• raw: raw values of the data
• ranom: anomalies from 11-day running mean
• ranom2: anomalies from 15-day running mean
• rmean2: 15-day running mean
• hbudget: Anomalous budget terms of moist static energy

2) Phase composite OLR data using the MJO index (“K12com” directory)

3) Data file describing the number of MJO events on each date when the eastward propagation is completed (“others” directory)

— OBS
This directory stores the ERA5 reanalysis data (“ERA5” directory), SST, and OLR data (“others” directory). The “others” directory includes the two types of data: climatology and raw values.

— Drawscript
This directory stores NCL (NCAR Command Language; version 6.6.2) scripts needed to create all the figures in the main text and supplementary materials. The names of the files (XX of “XX.ncl”) correspond to the names of the figures. More detailed descriptions are as follows:

• Figure1AB.ncl: Script for Time-longitude digagrams of MJO convection for November and December in 2018 (hereafter, denoted as Nov-MJO and Dec-MJO).
• Figure1CD.ncl: Script for the histogram of the timing of MJO propagation in NICAM ensemble simulations.
• Figure1EFG.ncl: Script for time-logitude diagrams of CWV and OLR related to the representative MJO regimes.
• Figure2A.ncl: Script for maps of the OLR evolution associated with the two regimes simulated in NICAM ensemble simulations.
• Figure2B.ncl: Same as Figure2A.ncl, but for the meridional-vertical sections of circulations.
• Figure2C.ncl: Script for the map of the climatology and ensemble mean of observed and simulated OLR, respectively.
• Figure2D.ncl: Script for the map of observed SSTs.
• Figure3A.ncl: Script for the histogram of the timing of MJO propagation in Dec-MJO control and sensitivity experiments.
• Figure3BC.ncl: Same as Figure3A.ncl, but for Nov-MJO control and sensitivity experiments.
• Figure4A.ncl: Script for the map of upper-tropospheric dynamics (QGPV and Q-vector), water vapor, and lower-troposphericy eddy kinetic energy before the observed Dec-MJO propagation.
• Figure4B.ncl: Same as Figure4A.ncl, but for the NICAM simulation.
• Figure4C.ncl: Script for the map of upper-tropospheric extratropical Rossby waves before the observed Dec-MJO propagation.
• Figure4D.ncl: Same as Figure4C.ncl, but for the NICAM simulation.
• Figure4E.ncl: Script for the map of differences in background upper-tropospheric QGPV and Rossby-wave refractive index between the two different Dec-MJO propagation regimes.
• Figure4F.ncl: Script for the zonal-vertical section of the differences in MJO circulations between the two different Dec-MJO propagation regimes.
• figureS1.ncl: Script for the phase composite of MJO convection.
• figureS2ac.ncl: Script for the maps of observed OLR evolution associated with Nov-MJO and Dec-MJO propagation.
• figureS2bd.ncl: Same as figureS2ac.ncl, but for the NICAM simulations.
• figureS3ab.ncl: Script for the comparisons of MSE budgets in the simulated Dec-MJO propagation.
• figureS3cd.ncl: Script for the maps of surface heat fluxes, OLR, and background winds for the second regime of Dec-MJO propagation in the NICAM simulations.
• figureS4.ncl: Script for the EKE budget analysis for the westward-propagating synoptic-scale wave in the observations, Dec- 1 and Dec-2 regimes.

File: Takasuka_etal_2025_Science_Part2.tar.gz

Description: All the data have the netCDF format. The directory structure is as follows.

— data/OBS
This directory stores the three files.

• ex.200.day.clima.1979-2022.nc 
• ey.200.day.clima.1979-2022.nc
• uwnd.200.day.clima.1979-2022.nc
  The former two files include the daily climatology of x- and y-components of 200-hPa E vector (m²/s²), and the last file includes that of 200-hPa zonal winds (m/s).

— scripts
This directory stores NCL (NCAR Command Language; version 6.6.2) scripts needed to create all the figures in the main text and supplementary materials. The names of the files (XX of “XX.ncl”) corresponds to the names of the figures. More detailed descriptions are as follows:

• Figure1CD.ncl: Updated script of the Figure1CD.ncl in Takasuka_etal_2025_Science.tar.gz.
• Figure2B.ncl: Updated script of the Figure2B.ncl in Takasuka_etal_2025_Science.tar.gz.
• Figure4A-D.ncl: Scripts for the decomposition of the Figure4A.ncl and Figure4B.ncl in Takasuka_etal_2025_Science.tar.gz.
• Figure5A-D.ncl: Same as Figure 4C, 4D, 4E, 4F.ncl in Takasuka_etal_2025_Science.tar.gz.
• Figure6AB.ncl: Scripts for the map of the climatological upper-tropospheric zonal winds during Nov-MJO and Dec-MJO propagation and its difference.
• Figure6C.ncl: Script for the map of the difference in climatological upper-tropospheric E vectors and zonal winds between Nov-MJO and Dec-MJO periods.
• figureS2bde.ncl: Updated scripts of the figureS2*.ncl in Takasuka_etal_2025_Science.tar.gz.
• figureS5.ncl: Script for comparisons of composite OLR anomalies averaged over the Indian Ocean during the initial phase of MJO convection between the Dec-1, Dec-2 and Nov-1 regimes.
• figureS6.ncl: Script for the tropical-extratropical dynamic evolution for observed Nov-MJO and/or the Nov-1 regime.