Arctic Oscillation (AO)

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

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.

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. Anomalies are with respect to 1950-2001, but the time series has not been standardized.

table organized by years and calendar months

3-column table (year, month, data value)

One-column table (data only)

Monthly-means * 100.

       jan  feb  mar  apr  may  jun  jul  aug  sep  oct  nov  dec
 1899   77  -19 -112  -10  -33  -21  -39  -63    5   13   65 -176
 1900  -84 -260 -160   58   32  -23  -23  -13  117   27  -22   72
 1901   97 -109   31   67  -32   23  -15    5  -14  -58   -1 -119
 1902   41 -151   25 -139  -63 -154  -64 -104  -37   -3  -26   60
 1903   69  350  204  -72   -4 -176  -59  -27    0  -57   44  -84
 1904  129   30   -4  124   41  -34  -28  -73  -56  -40   26   23
 1905  175   90   32 -152   65   -8   -3  -55   -5 -106  -13   91
 1906   30  -70   45   53 -123 -106  -30 -101  -18  -27 -201    9
 1907   31   66  186  -30 -119  -79 -126  -39  -41 -103  -40 -103
 1908   97   29   38  -47   49  -37  -58  -24   17  -45  -50  -15
 1909   45  -38 -259   17 -122  -66   38   57  -71  -91  -38 -111
 1910  189   85    9  -20  -41  -35  -45  -87  -11   28 -306  -85
 1911  110  171   74   75   50  -27  -65  -47    4  -55   40  -10
 1912  -67 -102   36   63   35  -64  -60 -102 -143  -69    7  104
 1913   63  104  299   38   10   43  -70  -64  -85  -70  126   32
 1914  139  146   20  145  164   48  -48  -45  -11  -76   38   83
 1915 -123  -60 -226   82  -88  -74  -77 -103 -109 -122 -166 -120
 1916  265  101 -222  -37  -38  -82   18   -7  -26  117   23 -255
 1917 -128    5  -28 -148 -134   19  -10  -48  133   22   69 -146
 1918 -197  284   82  -34   68   38 -163   -5    2  -30  -10  -29
 1919  -97 -171  -84   27  -75   24   -6   29   47 -139 -142   43
 1920  116  155  283 -102   19  -55   37  -65  -31 -110  109 -112
 1921  185  -23  198  -28   -2  -69    7  -18  -40  -39 -205  108
 1922  -90  146   18  -56   29   33  -16  -76  -32 -184  -11   36
 1923  168  -36   28  -13  -36  -29    6  -60   -7    2  -90   36
 1924   22 -113 -213  -56  -11  -35   75   26   58  -15   54  137
 1925  228   39  -84  125  -36   12  -49   -3   38  -40  -28 -125
 1926   25   11   69   10 -113 -123   64   15   10 -134  -21  -36
 1927  104  -25  128   95  -38  -18  -13  -29  -53  -62   38 -173
 1928  222  166  -75    5  -86  -68   45  -39    2   14    1  -16
 1929 -281 -102  159   -2   -2  -67   -2  -32  -15   41    5   61
 1930  137   40   55  -88   42   37  -21  -61 -102  -42   64  -34
 1931 -132  -48 -182   -1  -42  -64   -4  -32  -10   38   53  128
 1932  258    1 -162  -46  -66  -68  -20    4   51   -4   61  112
 1933   66 -188  -34  -34  -24   -4   53   96  -79  -97   11  -16
 1934  157  163  -20  -37  119  -42  -29  -21  -80   18  -33  -65
 1935   29  266    1 -147  -87  -30   88   35  -20   65  -36 -273
 1936 -249 -309  -60  -37  -12    5  -18   11  -14   23   53  214
 1937  127   77 -248   19   40   25  -12   39   79  -45 -106 -223
 1938   84   62  277   70   14   84   32   41   24   72   72  -96
 1939 -103  215   12   46    2  -21  -32   -2   15  -30   31  -31
 1940 -355  -90 -129  -11  -41  -16  -15   45   -6  -68   91   -3
 1941 -145 -183 -110  -80   25   42   46  -23    8   31   14   74
 1942  -41 -228  -20   14   21  -37   24   28   69  -14   21   37
 1943  -78  257  144  240   77  -21   -4  -83    9  -21  -29   56
 1944  155   39  -22   15   80  -12  -36   76   49   49 -150 -999
 1945 -275   -7   78   43  -17  -57  -20   77   -8   48  -23 -244
 1946   58  -83  -16  115  -62   11   31    6  -22   25   17 -101
 1947   25 -523 -121  190   25  -38   55   -7  100   78 -277 -178
 1948   62  111  303  114  -29  -52   -6   16   33   97   84   69
 1949  221  221  -25  164  -35  -56    8   14  -30   94 -118  -75
 1950   28   80   44   33   31   63  -52  -51   47  -14  -55 -175
 1951   32  -15 -195  -74  -57  -80   21  -23  -59    6   41  224
 1952   63 -163 -199   68  -73  -45   58   21  -26  -45 -180 -155
 1953  -43   31  167 -104  -42    8   53   27  101   11   71  141
 1954   31   62   87   40 -164  -16   45   17   39   63   14   31
 1955  -58 -156 -172    2    7  -29   63  106   39   15 -120  -40
 1956 -106 -179   99  -93  146   23  -16  -52    6  108   -2    2
 1957  272 -162 -172   37  -82  -64  -49   21  -74   96 -105  103
 1958  -95 -173 -255  -29  -34 -116  -56  -71   14   57   30 -165
 1959 -189  315  190    1  -29   -4   19  -70   -7  -27 -126    0
 1960 -222 -185 -153  -35  -85    2  -52  -93  -34 -122  -50  -20
 1961  -92  120   53  -45   20   75   -6    9   91   -8   10 -179
 1962  196   10 -288  108  -10   18  -91   20   -6   -7  -87  -47
 1963 -286 -107   78  -52   79  -65  -25  -60   38  101  -33  -66
 1964  112  -34  -33   35   88   18   88 -113  -28   18  -37  -28
 1965  -70 -187  -73   45  -22    5  -48  -12  -69   45 -137   -2
 1966 -290 -136  -90 -221  113   49    9  -87   25 -139   18 -151
 1967   -2  173  204  155    2   64   26  -10   46  123   43  -33
 1968  -32 -157  224   28  -22   35  -61  -55 -108 -113 -182  -83
 1969 -308 -291 -140   64  -60  -23   45  -68    7    2   44 -139
 1970 -210  -87 -201   14   47   99   21  -15    4  -16   44  -22
 1971    1  -77  -88  -58   84  -69  -42   96   27  105   55   79
 1972   54   25   13   78   19  -13  -46   15  -90   30  -38  153
 1973  203  120   98 -137   13   55   41   33   28   21    0   18
 1974   54  -34  -13   50  -55  -14   43  -40  -17 -112  -28   63
 1975  193   85   42   23  -53  -42   55   27  125   11   88  162
 1976   51  222   86   51   11   26   -7   86  -49  -95   24 -192
 1977 -338 -147   45  124   24  -25  -44 -122   65   -9   64   -1
 1978   44 -237   84  -91    4   49  -49  -17   -6   81  285  -91
 1979 -185  -48  -62 -144  -20   74   13  -53    4 -118   57  158
 1980 -172   -7 -122  -30 -107   56  -52  -26   35  -64 -105    4
 1981   78   24 -132   56   34  -50   60   -8 -106 -162    5 -104
 1982  -59  135  124  138  -31 -117   18   33   60  -51   84  134
 1983  204  -85    2  -89  -49   33   29  119    2  111  -10   43
 1984  116   25 -193  -29   51   -4    4   65  -34  -48  -67   68
 1985 -222 -149   73   47  -40  -47  -31   -6   -2   88 -113 -179
 1986    1 -205  259   -1   36   63   -1  -67    2  131  101   55
 1987  -31 -102 -143   52   37  -72  -31  -85   24  -13  -36  -33
 1988   85  -67   -7  -48  -78   15  -11   32  102    6   33  200
 1989  362  360  174  -31   84   29   96   65   87   80   15  -35
 1990  135  341  355  191  121   23  -18   -3  -18   47   39  143
 1991  117   -9  -36   59   60  -27   -7   97   -3  -37   53  204
 1992  164  176  138  -68  141  -24   27   55  -67  -43   86  181
 1993  406  112  133  -27 -148  -60  -51  -34  -35  -55  133   -7
 1994  -14  -48  203   17    4  145   50   89   -1    8  187  117
 1995   54  179   53  -99  -84   -6  -11   65  -25   -4  -43 -147
 1996  -61   78 -111 -142  -30   36   75   24 -112   -7   17 -153
 1997   35  253  130   51  -95  -80  -22   30   37  -90  -31   29
 1998 -156   72   17   -2   52  -90  -26   60  -92    0 -130  151
 1999   41   95 -147   16   17   79   -1  -46   12  -25   89  102
 2000  138  182    4  -26   99   56  -58   14   58   15 -150 -226
 2001  -26  -25 -155   87   46  -17    6   59  -55   46  130  -96
 2002  196  152  116   54   42   59

November 2004
Todd Mitchell ( mitchell@atmos.washington.edu )

JISAO data