JISAO data

Global-SST ENSO index, 1817 - February 2011

Introduction and analyses | Digital values

The index is the average SST anomaly equatorward of 20-degrees latitude (north and south) minus the average SST poleward of 20-degrees, and it captures the low-frequency part of the El Niño / Southern Oscillation phenomenon. Anomalies are with respect to the period 1950-79. The number of observations contributing is at least 1000 in each month and year beginning in 1850s.

The input data is the International Comprehensive Ocean-Atmosphere DataSet (ICOADS) version 2.5 for 1800-2007 and the "National Centers for Environmental Prediction near-real-time" (also an ICOADS product) for 2008 to present.

The choice to calculate the index as the difference of two time series removes a spurious step-jump in SST observations at the onset of World War II that is associated with changes in measurement practices. (This jump is discussed in this link.) The difference also removes the common portion of the trend in SST.

See caption
Big GIF | JPG | PDF | PNG | PS

See caption
Big GIF | JPG | PDF | PNG | PS
The time series is unfiltered in this plot.


Data:
The time series (degrees C) is available in ASCII format.
  • 7-column table: year, calendar month, index value (C), tropical mean (C, 20N-20S mean), extratropical mean (C, 20N-90N and 20S-90S), tropical number of observations, extratropical number of observations, respectively.
  • 1-column table of the index value (C)
  • Year-month table

    Digital values:
    The anomalies are in hundredths of a degree Celcius, for example "-73" is -0.73. Missing values are blank.

           jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec
     1817                                          -73      -101  -83
     1818                                                            
     1819                                                            
     1820                                    -122                 -31
     1821                                                            
     1822                      -25  -23  -58  188   31      -153  199
     1823 -106  155   25  -51  -86      -132                         
     1824                      208                           -67   30
     1825                  90                                        
     1826 -269                 -78   29                              
     1827 -119      -167       -69   84  -76   15  146   -8 -120   99
     1828       -75   55  -72  175  -55  -77  -17  107   13        75
     1829    8  -39  -26   16  -67 -246 -196 -108 -185 -137  -44     
     1830      -189      -162                   4   57      -123   41
     1831   -8        77   57   38 -140  110  -12                  -9
     1832   13  -67                      -22       -87   -4          
     1833       -24   13            -52  -88  -11           -214    0
     1834       -25  -16  -68    2  -96            171  -39        73
     1835      -348 -360  -46                  89   36  202  -53    2
     1836 -106 -131  -16    7  -79            -21  -40               
     1837  164        58  124  -75  -52  -86            -31          
     1838  149   70 -144  -23   61  -56  116                       93
     1839                           -60                              
     1840              2  -81      -119                          -134
     1841  -22 -161  -68                 -13  218   22   -4   63  339
     1842   10 -148                                                  
     1843                           -15           -101               
     1844                      -34   25 -193                -259     
     1845   14  -45 -187   23  -78   -6 -103  -29    8   20   35   17
     1846 -195   78   12      -134   -6  -18    9 -118  -18   87   76
     1847   33  -86   38  -93 -111 -144  -77 -120        13   89   17
     1848  -67  -66 -135  -37 -116  -81  -31   -5  -12   27  -37   -3
     1849   -8   -5    2  -17  -14    0   -9  -44    1   26    7   -6
     1850   15   14  -15  -18   29   31   31   20   37   -2   25   18
     1851    0  -13  -17  -20  -34   10   32   25   29   -7   -5   22
     1852   -2    6  -17    1    3   24   33   31    3   24   31   -6
     1853   21   17   16  -14  -19  -25   33    0   23   33   40   14
     1854    1    9   20   11   28   26    4   -1   11   47   34   28
     1855   -6   -2    4   13   18  -13    6    6   19    9   15   -2
     1856  -17   19   -2  -19   17   19    9   14   60   44   13   30
     1857   -2  -19  -58  -29  -14  -16   31   11   16   28  -16   -3
     1858   -9  -11   -6  -27  -15   21    3   22   41   41   37   -7
     1859   17   -8    3  -12   53   42   39   48    3   -4    8    6
     1860  -46  -17  -24   12  -20    8    6   28   32   20  -29  -24
     1861  -28  -40    9  -25  -24  -15   31   15   13   28   17    6
     1862  -10   -7    0   11   49    8   46   82   41   58  -10  -10
     1863  -37   -1  -25  -30   13   20   -1   23   54   44    1  -18
     1864  -36  -69  -27  -28   -9   -6   27   -1   35   -1   26  -18
     1865  -15   13   10   43   39   33   19   50   60   15   46   15
     1866   20    4   38   54   12   26   17   59   33   10   25  -47
     1867  -14   27   24    3   57   38   31   78   29   34   23   32
     1868   15   30   25   10   42   20    7   19   61   33   47   -1
     1869  -14  -26   28   21   52    4   25   54   35   26   15   23
     1870    1   30    2   -7    1    5   -3    7   29   25  -62   -3
     1871  -28   -3   10    8   29   -3   39   37   29   50    1   18
     1872  -18    9  -34  -21   -2   23    8   37   11    6  -14  -20
     1873  -20  -16   -4   23   25   -8  -21   26   51   22    3    0
     1874   -9  -18   -5  -41   16    2    6  -12   15  -18  -24    3
     1875    0   17  -13  -34  -22   -8   19  -36    4   27   43   40
     1876   27   15   38   25   17   13    6   -4  -23    7   21    6
     1877   -3  -26  -23   14   15   28   43   40   61   56   14   43
     1878   85   66   34   53   59   61   54   32   13   34   42    7
     1879   -4   11  -17   -8    0   12   -1   17   -4  -20    9  -12
     1880  -19    8    4  -13    6  -14  -41   -6   -9    4    4   10
     1881   -6    2   24   27   30    9   38   35   41   25   38   17
     1882    0    1   -1   20   -2  -37  -27    2    4    1    1  -11
     1883   -2  -36  -17  -27    6   -6   -6   -9    0   -8  -28  -26
     1884  -38  -17  -33  -23    3    9    5    6   31    8   10    8
     1885    9   16    0    6    7  -15   -5   -7   22   54   30   21
     1886   13    6   18   19   33    6    8    9   24    0   -2  -19
     1887   -7    0   -8  -21  -17  -38  -14  -16   12   13   35   11
     1888   18    6   45   30   28    4   39   26   35   42   46   47
     1889   56   38   37   40   30   18   31   24   30    6  -14  -12
     1890  -15  -27  -13  -23  -19  -42  -18  -31  -37  -28  -39  -24
     1891  -15   -4   -1   11   13    7    6    1   -8   16   13   11
     1892   -5   -1    6  -19  -18  -25  -16  -36  -28  -28  -46    5
     1893  -15  -40  -33  -25  -24  -27   -7   -6  -12   -9  -10  -16
     1894  -30  -23  -25  -31  -25  -20  -27  -28  -11   -1  -11   -6
     1895    3   12   13   -1    5  -12   -5   20   32   36   34   35
     1896   25   15   20   22    8    5    5   18   26   42   60   54
     1897   54   37   33   41   34   19   40   38   41   49   28    6
     1898   -3  -23  -20  -20   -9  -20  -30  -40   -4    5   17   -2
     1899  -19  -30  -27  -23   -2  -19  -18   12    3   16   23   47
     1900   22   28   24   30   23   19   24   12    3   29   22   44
     1901   21   12   33   25    0   -7   -9   15    5    9   36   24
     1902   -6    2  -13   13   14   14   44   36   15   23   27   29
     1903   30   21    0    8   15   23   17   32    9   23   -2  -18
     1904  -31  -40  -29  -41  -22  -29  -11   -7   12    3   11   23
     1905    7   19   -2  -10   21   -1  -17    9   11   30   33   16
     1906   15   33   19   -1   11   -3   -9   -1    9   -6    9    5
     1907   -9    2  -19  -12  -16   -5   -6   -4    0   10   24   16
     1908   16   -1  -26  -18  -15  -36  -31  -14    0    7   -6   -5
     1909   -4    2    9   -8   -2  -17   -1    1    8   -3    4    4
     1910    7    1   -3   -8    5   12   21    5   11    5    4    4
     1911   -4   -4  -11  -24  -16  -20  -10  -15  -17    3    8    6
     1912   27   16    1   21    0   19   15   21   42   31   23   11
     1913    4    9   -3  -17   -1   14   16   13   15   15   29   40
     1914   30   18    5    7   -2   -5   -5   14   20   11   39   32
     1915   30   35   39   19   29   15   23   15   19    6    9   19
     1916   26    3    7   -9    7  -16    0   -9  -18  -17  -16  -29
     1917  -17   -2  -30  -23  -14   -5   -1   -1  -19  -22   -4   -6
     1918   -1  -26  -22  -41  -18  -24  -20    6    4   30   64   58
     1919   52   67   30   15   17   -7   -5    7    3    2    5   15
     1920   14    7   22  -17  -25  -19  -20  -14   -6   -1    4   15
     1921   19   -3  -23  -16  -12  -24   -9   -7    4   -8    0   29
     1922   12   16    1  -12    4  -11  -17   -4   -5    3   11    6
     1923    7   -8  -21  -15  -10   -5   -1  -10    6   22   25   33
     1924   28   43   35   26   16   -8    6  -11    4   -4   -1   -5
     1925  -14  -25  -17  -13   -4  -12   19   13   14   10   35   41
     1926   40   43   36   35   30   31   38   23   29   17   23   24
     1927   12   29   13   -2   -9    5   -1   -4   25   22   32   57
     1928   38   40   17    7   11    2  -15  -11   -4   -4    9   21
     1929   19   17   19    9   -8  -13   -8   -2    5   15   12   21
     1930   10   16    9    6  -18  -16  -21    4   11   33   41   36
     1931   52   48   60   48   49   29   42   12   24   23   18   17
     1932    2    1   20   18   17    9  -12   12    3   -9    8    9
     1933    8   17   17   -7    2  -15  -10  -23  -12  -18   -8    2
     1934   -7   -5  -23  -17  -27  -33  -17    5    0    7    2    4
     1935    7    3    0  -14    4   -7  -14    7    2    3   15   24
     1936   23   24   26   20   10  -17  -11    7    8   13   13   20
     1937   10   15   24   13   10    6  -10   -8   -3    3   19   31
     1938   19   28    8  -17  -20  -39  -27  -23  -19  -11  -13   -7
     1939   -4  -17  -23   -7   -6   -7   -7   -9  -12  -36   -7   22
     1940   41   44   40   27   36   17   10   24   35   30   35   33
     1941   51   53   55   36   32   50   39   59   25   46   33   37
     1942   39   31   11   15    9    0  -22  -21  -10  -14  -18  -16
     1943  -17  -19  -28  -43  -17  -17  -17   -7   -1  -15  -18  -24
     1944  -30  -17   -9    3   -7   -1   27   13   14   -2   -4    6
     1945   31   16  -20   -1   -6   14   -6    9    4  -14  -12    6
     1946    9   30   26    9  -16   -2  -22   -1  -19  -15   -8   22
     1947   19   25   31   -3    1   11    0   -6   -2    0   -5    6
     1948    3   30   13    9   -5   -5   -4   -7  -15  -13  -12    3
     1949  -37  -14  -18  -18  -20  -10   -3   -3  -19  -21  -36  -30
     1950  -20  -34  -25  -29  -38  -39  -41  -41  -38  -33  -37  -44
     1951  -36  -35  -32  -23  -10  -19    1   -6   13   23   25   13
     1952   -1   -3    2    6   -1  -16  -25  -31  -12  -20  -26   -2
     1953    9    3    6    1   -2   11    6    7    1   -6    6    4
     1954   -6   -2   -7  -11  -15  -13  -24   -5  -25  -24  -33  -35
     1955  -15  -35  -32  -42  -46  -44  -29  -22  -14  -30  -37  -34
     1956  -28  -29  -24  -27  -31  -25  -32  -18  -24  -32  -22  -11
     1957  -18   -8    3    7   23   24   13   13   11   16   18   24
     1958   28   46   29   28   18    8   14    7    3   -4   -2   -1
     1959   14   14   13   14   10    4   -9   -8   -8    0    5    2
     1960    6    0   15    9   15   -2   -5   -6   -1   -5   -5   13
     1961    7   12   -6   -4  -14  -15  -29  -26  -25  -27  -18  -10
     1962  -15  -17   -8  -14  -15   -2   -7    3  -14  -11   -2   -7
     1963    8   12   16   20   15   17   22   27   23   29   33   37
     1964   47   36   25   13   -3   -3   10    1   -1   -8  -11  -19
     1965  -20    2    7   19   26   17   15   28   32   33   38   41
     1966   33   38   34   23   20   23   31   18   17   15   13    8
     1967    3   -8  -12    3    2   -5  -18  -33  -25  -28  -32   -6
     1968  -15   -7   -8  -11  -14   10   17   19   17   27   23   24
     1969   34   38   44   50   49   39   33   21   29   44   39   39
     1970   41   30   36   20   21    7   13   -4   -5  -13  -16  -25
     1971  -23  -23  -23  -14  -10  -18  -21  -13    3  -13  -18  -25
     1972  -14    5  -11    3    5   17   24   40   41   59   52   49
     1973   44   28   19   11   10    9   12    8    9    0  -11  -19
     1974  -47  -40  -33  -29  -13   -6    5    6   -8  -19  -14  -22
     1975  -23  -20  -24  -17  -25  -22  -12  -18  -31  -29  -36  -43
     1976  -43  -31  -31  -21   -7    4    6   16   24   34   37   11
     1977   16    7   -1   -4   10   15    9    9   10   14   22   20
     1978   25   12   12    1    0    5    7    4  -11   -2   -4    0
     1979    9    7   16   19   19   18   12    4   10   12   15   19
     1980   16   13   14   19   30   20   17   21   26   28   26   14
     1981    4   -2    3   -3    7    1   13   12   21   41   29   20
     1982   15   15   10   18   24   31   26   35   44   47   48   54
     1983   44   55   55   46   44   56   51   47   33   19    7   17
     1984   14   14   28   15    8   -1   13   10   24   15    7   -7
     1985   -7    0   -8   -8  -13  -13    7   15    8    1   14   10
     1986    0   12    2    6   11   16   31   21   22   26   36   25
     1987   22   20   36   30   58   59   51   54   54   69   67   49
     1988   42   35   37   31   21    7   10   19   20    4    4   -6
     1989  -18  -15  -20  -25  -20  -21    2   -5    3   12    4   11
     1990   -1   18    5    5    6    6    5    8    7   14    8   10
     1991   17    7    7   -2   17   27   25   26   21   21   22   27
     1992   19   19   10   23   34   23   31   27   29   29   13    2
     1993   -3    2    6   16   28   29   34   24   31   29   37   33
     1994   28   19   16   15   14   14   -3   -1    5   22   14   17
     1995   21   28   21   23   26   32   27   19   19    5   14   14
     1996    5    8   12    4    2   16   29   17   23   23   15    1
     1997   -6  -17  -11    2   18   23   36   40   46   57   73   75
     1998   66   70   63   38   34   20   12    9   16    1  -13  -13
     1999  -27  -26  -22  -28  -23  -30   -1  -12  -11  -15  -23  -19
     2000  -21  -15  -20  -24  -23  -33  -18   -3    2   -3   -1  -20
     2001   -9  -20   -6    2    7   -8   -5   -3   -5   -2  -13   -8
     2002    1   -3    6   12   12   20   17    8   15   21   33   50
     2003   38   36   25   17    5    0   15   20   14   28   27   23
     2004   21   15    9    6   -9  -13  -16   -7   20   18   23   33
     2005   29   20   27   15   23   -1   -5    0   -1   -3  -10   -3
     2006   -2    3    1   -1   11    9    4    7   19   23   31   36
     2007   28   21   11   12    8   17   15    9   -1  -11  -19   -8
     2008  -12  -17  -20  -16  -16  -19  -11    6   15   12   10   -1
     2009    1   -4    2   -2   14   11   18   32   38   33   35   41
     2010   40   42   46   43   40   22    3   -9  -12   -6   -7   -4
     2011  -18  -10                                                  
    
    An old version of this index is linked here.


    February 2011
    Todd Mitchell ( mitchell@atmos.washington.edu )
    JISAO data