These files are updated on a regular basis (near daily and monthly)
Please note: The Southern Oscillation Index (SOI) used by this site is derived from a climatic base period of 1887 to 1989. The National Centre (NCC) calculates the SOI from a 1933-1992 base period. Long Paddock will continue to provide 1887-1989 base period SOI data as the SOI phase maps are based on this data.
The file called 'MonthlySOIPhase1887-1989Base' contains a column of numbers under the heading 'Phase'. The five Phases of the SOI are as follows: