The National Centers for Environmental Prediction (NCEP) Climate Prediction Center calculates the SOI from Tahiti and Darwin Sea-Level Pressure (SLP) as follows:
SOI(month,year) = ( T(month,year) - D(month,year) )
-----------------------------------
S
where:
Reference:
Chelliah, M., 1990: The global climate for June-August 1989: A season
of near normal conditions in the tropical Pacific. J. Climate,
3, 138-160
The time series is linked here in ASCII format. [In MATLAB, "load soi1866199.dat" will load the time series into a variable named "soi."]
The Tahiti and Darwin time series are obtained from the University of East Anglia for 1866-97 and from the NCEP Climate Prediction Center for 1998-99. The NCEP site also provides the most up-to-date values and analyses of the SOI. NCEP also uses data for the period 1951-80 to standardize their series so you can simply append their values to mine.
In the following table, the SOI values have been multiplied by 10, and missing values are indicated by blanks.
jan feb mar apr may jun jul aug sep oct nov dec 1866 -7 -2 -6 -4 1 -5 -4 4 -2 1 10 -2 1867 3 0 0 5 4 -3 4 3 1 -4 -7 -10 1868 -3 -5 -17 1 -12 -14 -5 -13 -14 -12 -15 6 1869 -24 -4 -5 15 13 10 13 8 1 9 6 4 1870 12 3 -7 2 -2 -7 1 9 0 -6 -8 -14 1871 -15 -2 -21 -3 -4 2 2 4 6 -1 0 11 1872 33 15 17 -5 11 16 22 9 34 19 30 31 1873 30 15 19 14 5 -21 -12 -5 -22 -17 -3 14 1874 12 -4 -4 6 10 -12 -2 8 22 22 5 13 1875 9 -1 -10 9 6 17 -6 -2 8 11 -14 -7 1876 14 13 -2 7 5 12 -6 11 11 -10 -4 -4 1877 -11 -19 -12 -25 -12 -28 -10 -9 -18 -17 -13 -17 1878 -13 -30 -20 -7 1 -4 15 12 18 10 13 21 1879 16 18 14 10 1 12 21 21 20 15 8 -9 1880 13 9 15 4 10 6 2 13 9 4 6 -3 1881 -11 -9 1 1 -4 -5 -6 -12 -15 -26 5 8 1882 -10 -3 4 0 5 -11 -22 -27 -16 -4 2 11 1883 8 9 -31 11 11 2 -11 0 -9 4 3 -21 1884 -18 -8 10 -11 1 6 -3 -7 -8 3 -3 -17 1885 -23 0 5 0 -3 -12 -5 -11 -4 -19 -16 5 1886 -1 0 2 3 5 3 6 12 14 13 9 16 1887 16 13 10 7 -4 3 5 3 5 4 -6 6 1888 -5 -4 -15 -18 -8 -14 -17 -10 -10 -16 -13 -4 1889 -35 -3 -33 0 -2 16 1 1 11 3 20 26 1890 27 14 15 5 3 3 -3 -5 9 2 1 -1 1891 20 -7 -12 4 0 -2 -6 -9 -11 0 -5 -6 1892 3 -15 11 6 8 14 7 4 0 9 -8 3 1893 12 9 4 9 12 14 18 7 13 7 8 -6 1894 26 13 9 7 -7 0 4 -14 -3 3 -8 1 1895 6 8 -2 8 3 -8 -8 -11 -6 -8 -6 -11 1896 1 5 -9 -7 -27 -19 -14 -23 -20 -21 -13 -19 1897 -17 -11 -21 -14 -13 -1 -2 0 0 1 -9 11 1898 9 6 20 9 -1 -3 6 7 9 4 2 4 1899 17 11 14 3 -6 -9 -6 -12 -2 6 15 -5 1900 -10 -10 -31 -14 -6 20 9 6 -19 -20 -7 -8 1901 -1 3 10 4 0 14 14 9 -17 -25 -9 -4 1902 22 -4 13 6 7 1 1 -10 -19 -8 -4 -5 1903 -13 -15 19 14 6 -2 5 -1 9 3 0 18 1904 18 20 10 24 7 -7 -9 0 0 0 -18 2 1905 -13 -24 -36 -20 -12 -15 -21 -9 -8 -7 -18 -18 1906 -6 -12 -5 -6 -7 -4 6 14 19 8 19 3 1907 6 -3 -3 -6 -5 3 -1 -10 -1 -4 -5 7 1908 -12 11 -5 7 1 -4 13 2 19 7 1 -8 1909 -5 -5 -3 -11 1 17 10 8 0 3 7 4 1910 6 19 13 4 0 16 20 8 16 10 17 18 1911 3 0 3 1 -7 -10 -13 -13 -10 -13 -8 -3 1912 -14 -24 -12 -16 -10 -6 -1 -9 -5 -10 1 -11 1913 -6 -8 0 -5 -6 -4 -2 -9 -10 -11 -12 -10 1914 -7 2 10 -15 -9 -17 -10 -16 -16 -9 -6 3 1915 -34 -8 -25 -11 7 17 24 13 14 9 -16 10 1916 6 -7 -9 0 5 5 24 15 4 5 8 17 1917 6 13 19 17 18 15 27 33 31 15 19 27 1918 19 21 -3 13 8 -5 -14 -5 -8 -6 0 -11 1919 -21 -16 -17 -2 -6 -9 -9 -8 -6 -12 -12 -13 1920 1 -4 -6 0 -2 3 8 4 5 -6 -1 10 1921 15 7 11 -9 1 26 2 -8 5 9 7 9 1922 10 10 5 -4 -5 3 2 -2 5 5 7 13 1923 6 4 9 6 1 -1 -12 -19 -16 -7 -13 1 1924 -8 0 1 -12 9 5 7 9 8 7 10 5 1925 6 16 15 11 -1 -5 -14 -12 -7 -15 -10 -10 1926 -8 -21 -17 -5 -2 -7 -2 -9 1 3 0 6 1927 6 0 20 5 5 6 1 -7 0 -6 -9 8 1928 -13 13 14 9 -2 -7 -1 9 8 8 2 13 1929 20 22 5 3 -10 0 1 -1 0 7 9 6 1930 16 9 1 -3 2 -5 -5 -3 -7 3 1 -3 1931 9 -21 6 7 11 14 9 -5 4 -10 -3 9 1932 2 -5 -8 -18 0 -2 -16 -8 -10 -6 -6 2 1933 -16 5 -4 3 5 -4 3 -2 2 2 6 9 1934 8 -1 -2 4 -6 7 2 -24 -7 3 12 -4 1935 8 -8 12 2 -5 -3 -1 1 6 6 3 -6 1936 -3 -1 1 18 3 -2 3 -11 2 -1 -15 -1 1937 11 -8 5 1 0 1 -6 2 1 -4 -4 7 1938 9 3 -6 3 10 13 18 11 8 12 0 16 1939 22 9 12 7 -1 -2 8 -2 -10 -17 -9 -12 1940 -1 -7 -14 -7 -12 -16 -15 -20 -21 -19 -8 -38 1941 -13 -22 -14 -8 -6 -12 -20 -20 -9 -22 -10 -12 1942 -18 -7 -8 -4 4 5 -1 2 9 7 -5 16 1943 12 12 3 10 2 -7 2 6 5 8 2 -12 1944 -12 4 5 -4 -1 -4 -9 2 3 -10 -8 4 1945 6 7 14 -5 0 5 3 10 9 2 -4 7 1946 -4 4 -3 -7 -9 -9 -10 -6 -17 -14 -2 -8 1947 -7 -7 12 -4 -11 1 9 5 12 -3 8 5 1948 -5 -5 -7 2 3 -5 0 -6 -8 5 3 -8 1949 -10 1 5 1 -5 -10 -2 -6 2 4 -7 8 1950 5 21 19 12 6 20 20 11 7 16 10 27 1951 17 6 -8 -6 -10 -3 -14 -7 -13 -14 -10 -10 1952 -12 -11 0 -5 6 5 4 -4 -3 2 -1 -16 1953 2 -10 -8 -1 -22 -3 -1 -19 -15 -2 -4 -7 1954 6 -7 -3 4 2 -3 3 8 2 1 1 15 1955 -7 18 1 -5 9 11 17 13 15 15 14 11 1956 14 15 9 8 13 8 11 9 0 19 1 10 1957 6 -5 -4 0 -10 -2 1 -10 -11 -2 -12 -5 1958 -23 -10 -3 1 -10 -1 1 6 -4 -4 -6 -9 1959 -13 -20 8 3 2 -6 -5 -6 0 3 9 9 1960 0 -3 5 6 4 -3 4 5 6 -2 6 7 1961 -5 8 -26 7 1 -3 1 -1 1 -7 6 15 1962 22 -6 -3 2 9 3 -1 4 5 9 3 -1 1963 11 3 7 4 2 -8 -2 -5 -6 -15 -10 -15 1964 -6 -2 8 11 1 5 5 13 14 13 0 -6 1965 -7 0 2 -10 0 -11 -23 -13 -15 -13 -22 0 1966 -17 -7 -18 -6 -7 1 -2 2 -3 -4 -2 -7 1967 19 16 7 -2 -3 4 1 5 6 -2 -5 -9 1968 4 10 -6 -2 11 8 7 -2 -4 -4 -5 1 1969 -19 -11 0 -7 -6 -2 -8 -6 -12 -13 -2 3 1970 -15 -16 0 -4 1 7 -6 2 12 8 18 20 1971 3 19 21 17 7 1 1 13 16 17 6 1 1972 4 9 1 -4 -21 -11 -19 -10 -16 -12 -4 -16 1973 -5 -20 -1 -2 2 8 5 11 14 9 29 20 1974 27 20 22 8 9 1 11 5 13 7 -3 0 1975 -8 6 12 11 5 11 20 19 23 17 12 23 1976 15 16 13 1 2 -1 -13 -13 -14 2 8 -6 1977 -6 9 -13 -7 -9 -15 -15 -13 -10 -14 -15 -14 1978 -4 -35 -8 -6 13 3 4 0 0 -7 -3 -2 1979 -6 8 -5 -4 3 4 13 -6 1 -4 -6 -10 1980 3 0 -12 -10 -3 -4 -2 0 -6 -3 -4 -3 1981 2 -6 -21 -4 7 8 8 4 6 -7 1 5 1982 12 -1 1 -3 -7 -16 -19 -25 -23 -22 -32 -28 1983 -41 -46 -34 -9 4 -4 -7 -2 10 3 -2 -1 1984 1 6 -9 2 0 -8 1 0 2 -6 1 -4 1985 -6 10 1 7 2 -9 -3 6 0 -7 -3 2 1986 9 -17 0 1 -5 7 2 -9 -6 5 -15 -18 1987 -9 -19 -20 -18 -17 -17 -18 -15 -12 -7 -1 -8 1988 -2 -9 1 -1 8 -2 11 14 21 14 19 12 1989 17 10 6 15 12 5 9 -8 6 6 -3 -6 1990 -2 -24 -11 0 11 0 5 -6 -8 -2 -6 -4 1991 6 -1 -14 -10 -15 -5 -1 -9 -18 -15 -8 -23 1992 -34 -14 -29 -14 0 -11 -7 0 0 -19 -8 -8 1993 -12 -13 -11 -16 -6 -14 -11 -15 -8 -16 -1 1 1994 -3 -1 -14 -17 -10 -9 -17 -18 -18 -16 -8 -15 1995 -6 -5 -1 -11 -7 -2 4 0 3 -3 0 -8 1996 10 0 6 6 1 10 6 3 6 3 -2 7 1997 5 16 -11 -12 -18 -20 -9 -20 -16 -18 -14 -12 1998 -33 -27 -35 -19 0 7 13 10 12 10 11 14 1999 20 8 9 14 1 -1