Creation of BEST index
Creation of time series
The time series is based on combining an atmospheric component of the ENSO phenomenon (the Southern Oscillation Index or "SOI") and an oceanic component (Nino 3.4 SST which is defined as the SST averaged over the region 5N-5S and 170W to 120W). The SOI index is taken from Phil Jones at the Climatic Research Unit of East Anglia, England on their data page where they have defined it for the time period 1855 through 1997. Later SOI values are from CPC. The Nino 3.4 SST index is taken from the GISST dataset (through April 1998). Later values are from the Reynolds SST dataset.
The monthly mean climatology for the period 1898-2000 is removed for all the data. After that, the values are standardized by month so that each month has a mean of 0 and a standard deviation of 1.0 for all years during the output time period. The the resulting SST and the SOI values are averaged for each month of the time series. Then, either a 3-month or a 5-month running mean is applied to both time series
Reading time series
To read the time series, you can use code similar to:do iy=1898,lastyear read(iunit,913)nyear,(index(iy,im),im=1,12) enddo 911 format(1x,i4,12(f6.1)) where index is a real array of (1898:1997,12) values of -9.99 are missing