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JISAO data
Arctic Oscillation (AO) time series, 1899 - June 2002

 Definition and analyses | Data
The AO is the dominant pattern of non-seasonal sea-level pressure (SLP) variations north of 20N, and it is characterized by SLP anomalies of one sign in the Arctic and anomalies of opposite sign centered about 37-45N. Additional information is available for the Arctic Oscillation (AO) and for the North Atlantic Oscillation (NAO), a close relative of the AO.

The following two figures are from Hodges (2000).

Fluctuations in the AO can be seen in the time series of SLP anomalies for the North Pole
AO time series plot for 1900-2000 shows strong shift to high index in mid-1980s.
PostScript | PDF

The "high index" of the AO is defined as periods of below normal Arctic SLP, enhanced surface westerlies in the north Atlantic, and warmer and wetter than normal conditions in northern Europe. This is depicted as the "warm phase" in the following figure. "Low index" AO conditions are described in the "cool phase" panel.
Both North Atlantic and North Pole views of AO high and low index conditions.
PostScript | PDF

Additional analyses of how the AO is manifested in precipitation and surface air temperatures anomalies are available through this link.
The following are two analyses of January-February-March means of the AO time series "AO_TREN_NCEP_Jan1899Current.ascii" on Dave Thompson's AO WWW page. The digital values of the JFM-means are provided at the bottom of the present page.

see caption
PostScript | JPEG | PNG
The JFM AO exhibits generally positive values from 1899 through 1939, negative values for 1940-88, and positive values for 1989-present. This index is standardized with respect to 1950-99.

JFM-mean AO for 1950-2002, see above caption
PostScript | JPEG | PNG
References:
  • Thompson, D. W. J., and J. M. Wallace, 1998: The Arctic Oscillation signature in the wintertime geopotential height and temperature fields. Geophys. Res. Lett., 25, No. 9, 1297-1300.
  • Hodges, G., 2000. The new cold war. Stalking arctic climate change by submarine. National Geographic, March, 30-41.
    Data: The time series here is "AO_TREN_NCEP_Jan1899Current.ascii" from     Dave Thompson's WWW site. seasonal-means | monthly-means

    January-February-March means, standardized with respect to 1950-99.

  • table organized by decade
  • 2-column table (year, data value)
  • 1-column table (data values only)

    JFM-means * 100.
    
        +0    1    2    3    4    5    6    7    8    9
 1890                                               -15
 1900 -143    6  -23  179   45   85    2   82   47  -71
 1910   81  102  -38  134   88 -116   42  -43   49 -100
 1920  159  104   22   47  -86   53   31   60   90  -63
 1930   67 -103   28  -44   86   85 -176  -12  122   36
 1940 -164 -125  -82   93   50  -57  -11 -176  137  120
 1950   44  -50  -85   45   52 -110  -53  -17 -149   91
 1960 -160   24  -23  -89   13  -94 -147  108   11 -211
 1970 -142  -46   27  121    3   92  103 -125  -30  -84
 1980  -86   -8   58   35  -14  -84   16  -78    4  257
 1990  238   21  137  187   41   82  -26  120  -19   -2
 2000   93  -59  133
    Monthly means. I believe that the standardization is for all calendar months, but I'm not sure for which years.
  • table organized by years and calendar months
  • 3-column table (year, month, data value)
  • 1-column table (data values only)

    Monthly-means * 100.
           jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec
 1899   83  -24 -128  -11  -33  -24  -38  -59    5   20   55 -175
 1900  -78 -265 -175   57   32  -26  -21   -9  117   34  -32   74
 1901  103 -114   16   67  -33   20  -14    8  -14  -51  -11 -118
 1902   47 -156   10 -140  -63 -157  -63 -100  -37    4  -36   61
 1903   74  346  189  -72   -5 -179  -58  -23    0  -50   34  -82
 1904  134   25  -19  123   41  -37  -27  -70  -56  -33   16   24
 1905  180   85   17 -153   65  -11   -2  -51   -5  -99  -23   92
 1906   36  -74   30   53 -124 -108  -29  -97  -18  -21 -211   11
 1907   37   62  170  -30 -120  -82 -125  -35  -42  -96  -50 -101
 1908  102   24   22  -47   48  -40  -57  -20   17  -38  -60  -13
 1909   50  -43 -275   17 -123  -69   39   61  -71  -84  -48 -109
 1910  194   80   -7  -20  -41  -37  -44  -83  -11   35 -316  -83
 1911  115  167   59   75   49  -30  -64  -43    4  -48   31   -9
 1912  -62 -107   20   63   35  -66  -58  -98 -143  -62   -3  105
 1913   68  100  284   38   10   40  -69  -60  -85  -63  116   33
 1914  145  141    4  145  164   45  -47  -41  -11  -69   28   85
 1915 -118  -65 -241   81  -88  -77  -75  -99 -109 -115 -176 -119
 1916  271   96 -237  -37  -38  -84   19   -3  -26  124   13 -254
 1917 -122    0  -44 -148 -135   17   -9  -44  133   29   59 -145
 1918 -192  280   67  -35   68   35 -162   -1    2  -23  -20  -27
 1919  -91 -176 -100   26  -75   21   -5   33   47 -132 -152   44
 1920  121  151  267 -103   18  -57   39  -61  -31 -103   99 -110
 1921  191  -27  182  -29   -2  -72    8  -14  -40  -32 -215  109
 1922  -85  141    2  -56   29   30  -15  -72  -32 -178  -21   37
 1923  174  -40   13  -13  -37  -32    7  -56   -7    9 -100   38
 1924   28 -117 -229  -57  -12  -38   76   30   58   -8   44  139
 1925  234   35 -100  125  -36    9  -48    1   37  -33  -38 -123
 1926   30    6   54   10 -113 -126   66   19   10 -127  -31  -34
 1927  110  -30  112   94  -38  -21  -12  -25  -53  -55   28 -171
 1928  228  162  -90    5  -86  -71   46  -35    2   21   -9  -15
 1929 -276 -106  143   -2   -2  -70   -1  -28  -15   48   -5   63
 1930  142   35   40  -88   42   35  -20  -57 -102  -35   54  -32
 1931 -126  -53 -197   -2  -43  -66   -3  -28  -10   45   43  129
 1932  264   -4 -178  -46  -66  -71  -19    8   51    3   51  114
 1933   72 -192  -50  -35  -24   -7   55  100  -80  -90    1  -14
 1934  162  159  -35  -38  118  -45  -28  -17  -81   25  -43  -63
 1935   34  262  -15 -148  -87  -33   89   39  -20   72  -46 -272
 1936 -244 -314  -76  -38  -13    3  -17   15  -14   30   43  215
 1937  133   72 -264   18   39   22  -11   43   79  -38 -116 -221
 1938   90   58  262   70   14   81   33   45   24   79   63  -95
 1939  -97  210   -4   46    1  -24  -31    2   15  -23   21  -30
 1940 -350  -95 -145  -11  -42  -19  -14   49   -7  -61   81   -2
 1941 -140 -187 -126  -81   25   39   48  -20    8   38    4   76
 1942  -36 -233  -35   14   21  -40   25   32   69   -8   11   39
 1943  -73  253  128  240   77  -23   -3  -79    9  -14  -38   58
 1944  161   34  -38   14   79  -15  -35   80   49   55 -160 -999
 1945 -269  -11   63   43  -18  -60  -19   81   -8   55  -33 -242
 1946   63  -87  -31  114  -63    8   32   10  -22   32    7  -99
 1947   31 -528 -136  190   25  -41   56   -3  100   85 -287 -177
 1948   68  107  287  114  -30  -55   -4   20   33  104   74   71
 1949  227  217  -40  164  -36  -59   10   18  -30  101 -128  -73
 1950   33   76   29   32   30   60  -51  -47   47   -7  -65 -174
 1951   38  -20 -211  -75  -58  -83   22  -19  -60   13   31  226
 1952   68 -168 -215   68  -73  -47   59   25  -26  -38 -190 -154
 1953  -37   26  152 -105  -42    6   55   31  101   18   62  143
 1954   37   57   71   40 -164  -19   47   20   39   70    4   33
 1955  -52 -161 -187    2    6  -32   64  110   39   22 -130  -39
 1956 -101 -184   83  -93  146   20  -15  -48    6  115  -11    3
 1957  278 -167 -188   37  -82  -67  -48   25  -74  103 -115  105
 1958  -90 -178 -271  -29  -34 -119  -55  -67   14   64   20 -163
 1959 -183  311  175    1  -30   -7   20  -66   -7  -20 -136    2
 1960 -217 -189 -169  -35  -86   -1  -51  -90  -34 -116  -60  -19
 1961  -86  116   38  -46   20   72   -5   13   91   -1    0 -178
 1962  202    6 -304  108  -11   15  -90   24   -6    0  -97  -46
 1963 -281 -112   63  -52   79  -67  -24  -56   38  108  -43  -64
 1964  117  -39  -49   35   88   15   89 -109  -28   25  -47  -26
 1965  -65 -192  -89   45  -22    2  -47   -8  -70   52 -147    0
 1966 -285 -141 -105 -222  112   46   10  -83   25 -132    8 -150
 1967    4  168  188  155    2   61   27   -7   46  130   33  -31
 1968  -27 -161  209   28  -22   32  -59  -51 -108 -107 -192  -81
 1969 -303 -296 -156   64  -60  -26   46  -64    7    9   35 -137
 1970 -205  -92 -217   14   46   96   22  -12    4   -9   34  -21
 1971    6  -82 -103  -58   84  -72  -41   99   27  112   45   81
 1972   59   20   -2   78   19  -16  -45   19  -91   37  -48  155
 1973  208  115   82 -137   12   52   42   37   28   28  -10   19
 1974   59  -38  -28   50  -56  -16   44  -36  -17 -105  -38   65
 1975  199   81   27   23  -53  -45   56   31  125   18   78  164
 1976   56  218   71   50   10   23   -5   90  -49  -88   15 -190
 1977 -333 -152   29  124   23  -28  -43 -118   65   -2   55    1
 1978   49 -241   69  -91    3   46  -48  -13   -6   88  275  -90
 1979 -180  -53  -78 -145  -20   72   14  -49    4 -111   47  160
 1980 -167  -12 -138  -31 -107   54  -51  -22   35  -57 -115    5
 1981   84   19 -148   55   34  -53   61   -4 -106 -155   -5 -102
 1982  -54  131  109  138  -32 -119   19   37   60  -44   75  136
 1983  210  -89  -14  -89  -50   30   30  123    2  118  -20   44
 1984  121   20 -209  -30   50   -7    5   69  -34  -41  -77   70
 1985 -217 -154   58   46  -41  -49  -30   -2   -2   95 -123 -177
 1986    6 -209  243   -1   36   60    1  -64    1  138   91   57
 1987  -25 -106 -158   52   36  -75  -30  -81   23   -6  -46  -31
 1988   91  -71  -22  -48  -78   13  -10   36  102   12   24  202
 1989  367  356  158  -31   83   26   97   69   87   87    5  -34
 1990  141  337  340  191  121   20  -17    1  -18   54   29  144
 1991  123  -14  -51   59   60  -30   -6  101   -4  -30   43  206
 1992  169  172  123  -68  140  -26   28   59  -67  -36   76  183
 1993  412  108  118  -27 -149  -63  -50  -30  -36  -48  123   -5
 1994   -8  -53  187   16    3  142   51   93   -1   15  177  119
 1995   60  174   38  -99  -85   -9  -10   69  -25    3  -53 -145
 1996  -55   73 -127 -142  -31   33   76   28 -112    0    7 -151
 1997   41  248  114   51  -96  -82  -21   34   37  -83  -41   31
 1998 -150   67    1   -2   51  -93  -25   64  -92    7 -140  153
 1999   47   90 -161   17   17   76   -1  -43   12  -19   77  104
 2000  142  177  -12  -27   98   52  -57   18   57   21 -161 -226
 2001  -21  -30 -171   87   45  -20    7   63  -56   53  121  -94
 2002  202  147  100   54   42   56
    February 2003
    Todd Mitchell ( mitchell@atmos.washington.edu )
    JISAO data