The Files YYYY_pc_MJJASO.dat contains the MISO indices where YYYY represents years [1998-2019].
The data is created based on IMD rainfall data for the months MAY to October [i.e. "MJJASO" ].

The First Column is the day index, the second column is the value of MISO1 index, 
the third column is the MISO2 index and the lat column is the MISO "phase" indexed from 1-8. 

References: 

(i) "Simulation and extended range prediction of monsoon intraseasonal oscillations in NCEP CFS/GFS version 2 framework" 
by Sahai et al  2013 (current Science). https://www.currentscience.ac.in/cs/Volumes/104/10/1394.pdf  (Fig.13)

(ii)"An Indian monsoon intraseasonal oscillations (MISO) index for real time monitoring and forecast verification"
Suhas, E., Neena, J.M. & Goswami, B.N. Clim Dyn (2013) 40: 2605. https://doi.org/10.1007/s00382-012-1462-5

Brief Description:
MISO1 and MISO2 is created in a way similar to the "RMM" indices used to observe and track the MJO.
The MISO1 and MISO2 indices are the first two principal components (PCs) of the extended EOF analysis based on IMD 0.25deg resolution data.
The lag used to create the co-variance matrix in the Extended EOFs is 15 days.

For further queries please email: sahai@tropmet.res.in