Summer North Atlantic Oscillation Reconstruction ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Summer North Atlantic Oscillation Reconstruction LAST UPDATE: 11/2009 (Original receipt by WDC Paleo) CONTRIBUTOR: Chris Folland, UK Met Office Hadley Centre IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2009-128 WDC PALEO CONTRIBUTION SERIES CITATION: Folland, C., et al. 2009. Summer North Atlantic Oscillation Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2009-128. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Folland, C.K., J. Knight, H.W. Linderholm, D. Fereday, S. Ineson, and J.W. Hurrell. 2009. The Summer North Atlantic Oscillation: Past, Present, and Future. Journal of Climate, Vol. 22, pp. 1082-1103. doi: 10.1175/2008JCLI2459.1 ABSTRACT: Summer climate in the North Atlantic-European sector possesses a principal pattern of year-to-year variability that is the parallel to the well-known North Atlantic Oscillation in winter. This summer North Atlantic Oscillation (SNAO) is defined here as the first empirical orthogonal function (EOF) of observed summertime extratropical North Atlantic pressure at mean sea level. It is shown to be characterized by a more northerly location and smaller spatial scale than its winter counterpart. The SNAO is also detected by cluster analysis and has a near-equivalent barotropic structure on daily and monthly time scales. Although of lesser amplitude than its wintertime counterpart, the SNAO exerts a strong influence on northern European rainfall, temperature, and cloudiness through changes in the position of the North Atlantic storm track. It is, therefore, of key importance in generating summer climate extremes, including flooding, drought, and heat stress in northwestern Europe. The El Nino-Southern Oscillation (ENSO) phenomenon is known to influence summertime European climate; however, interannual variations of the SNAO are only weakly influenced by ENSO. On interdecadal time scales, both modeling and observational results indicate that SNAO variations are partly related to the Atlantic multidecadal oscillation. It is shown that SNAO variations extend far back in time, as evidenced by reconstructions of SNAO variations back to 1706 using tree-ring records. Very long instrumental records, such as central England temperature, are used to validate the reconstruction. Finally, two climate models are shown to simulate the present-day SNAO and predict a trend toward a more positive index phase in the future under increasing greenhouse gas concentrations. This implies the long-term likelihood of increased summer drought for northwestern Europe. GEOGRAPHIC REGION: North Atlantic/Europe PERIOD OF RECORD: 1706 - 2009 AD FUNDING SOURCES: Joint Defra and MoD Programme, (Defra) GA01101 (MoD) CBC/2B/0417_Annex C5, Swedish Research Council (VR). DESCRIPTION: Tree ring reconstruction of summer (July-August) North Atlantic Oscillation (SNAO) reconstruction, defined here as the first empirical orthogonal function (EOF) of observed summertime extratropical North Atlantic pressure at mean sea level. Reconstruction based on 7 tree ring chronologies in Norway and the UK: Site Name Country Lat. N Lon. E DataType Time Span (years AD) Forfjorddalen Norway 68°48’ 15°44’ TRW 878-1994 Femundsmarka Norway 62°00’ 12°11’ TRW 1001-2000 Lofoten Norway 68°29’ 16°02’ MXD 1485-1978 Coulin United Kingdom 57°32’ 5°21’ TRW 1671-1978 Coulin United Kingdom 57°32’ 5°21’ MXD 1671-1978 Narvik Norway 68°29’ 17°44’ TRW 1702-1978 Inverey United Kingdom 53°00’ 3°35’ MXD 1706-1976 All sites except Femundsmarka, Norway are archived in the International Tree Ring Data Bank: http://www.ncdc.noaa.gov/paleo/treering.html DATA: Summer (July-August) North Atlantic Oscillation (SNAO) reconstruction Column 1: Year AD Column 2: SNAO reconstructed Column 3: SE+ Column 4: SE- Column 5: 10 year average SNAO reconstructed (sigma =3) Column 6: SNAO observed Column 7: 10 year average SNAO observed (sigma =3) Year SNAOrec SE+ SE- SNAOrec10yr SNAOobs SNAOobs10yr 1706 -5.008 1.582 -11.598 1707 -8.207 -1.617 -14.797 1708 -5.134 1.456 -11.724 1709 -11.513 -4.923 -18.103 1710 -4.234 2.356 -10.824 1711 -4.746 1.844 -11.336 1712 -1.338 5.252 -7.928 1713 -2.800 3.790 -9.390 1714 -2.882 3.708 -9.472 -4.813 1715 -6.212 0.378 -12.802 -5.008 1716 -6.212 0.378 -12.802 -5.263 1717 -8.222 -1.632 -14.812 -5.523 1718 -7.817 -1.227 -14.407 -5.732 1719 0.761 7.351 -5.829 -5.878 1720 -5.762 0.828 -12.352 -5.937 1721 -8.271 -1.681 -14.861 -5.869 1722 -13.210 -6.620 -19.800 -5.610 1723 -1.965 4.625 -8.555 -5.141 1724 -6.088 0.502 -12.678 -4.499 1725 -5.420 1.170 -12.010 -3.789 1726 -2.337 4.253 -8.927 -3.110 1727 5.323 11.913 -1.267 -2.568 1728 -1.211 5.379 -7.801 -2.194 1729 -3.921 2.669 -10.511 -1.916 1730 -5.020 1.570 -11.610 -1.643 1731 -3.055 3.535 -9.645 -1.314 1732 -2.173 4.417 -8.763 -0.996 1733 -0.623 5.967 -7.213 -0.726 1734 5.780 12.370 -0.810 -0.646 1735 3.696 10.286 -2.894 -0.844 1736 0.211 6.801 -6.379 -1.352 1737 -6.722 -0.132 -13.312 -2.056 1738 -2.368 4.222 -8.958 -2.851 1739 -1.278 5.312 -7.868 -3.592 1740 -9.400 -2.810 -15.990 -4.189 1741 -6.083 0.507 -12.673 -4.596 1742 -4.827 1.763 -11.417 -4.794 1743 -2.420 4.170 -9.010 -4.823 1744 -8.119 -1.529 -14.709 -4.701 1745 -5.234 1.356 -11.824 -4.497 1746 -5.535 1.055 -12.125 -4.297 1747 0.659 7.249 -5.931 -4.185 1748 -1.180 5.410 -7.770 -4.166 1749 -6.218 0.372 -12.808 -4.226 1750 -5.163 1.427 -11.753 -4.377 1751 -7.416 -0.826 -14.006 -4.514 1752 -3.090 3.500 -9.680 -4.617 1753 -1.763 4.827 -8.353 -4.633 1754 -6.704 -0.114 -13.294 -4.541 1755 -8.208 -1.618 -14.798 -4.298 1756 -3.278 3.312 -9.868 -3.906 1757 -2.080 4.510 -8.670 -3.354 1758 -8.975 -2.385 -15.565 -2.673 1759 2.944 9.534 -3.646 -1.953 1760 -0.306 6.284 -6.896 -1.256 1761 -1.300 5.290 -7.890 -0.673 1762 1.005 7.595 -5.585 -0.237 1763 2.787 9.377 -3.803 0.037 1764 -0.040 6.550 -6.630 0.171 1765 -1.762 4.828 -8.352 0.162 1766 1.515 8.105 -5.075 0.041 1767 0.185 6.775 -6.405 -0.139 1768 1.627 8.217 -4.963 -0.396 1769 -1.258 5.332 -7.848 -0.668 1770 -1.729 4.861 -8.319 -0.906 1771 -4.966 1.624 -11.556 -1.067 1772 1.763 8.353 -4.827 -1.115 1773 -1.056 5.534 -7.646 -1.033 1774 -4.243 2.347 -10.833 -0.857 1775 1.098 7.688 -5.492 -0.559 1776 -0.181 6.409 -6.771 -0.200 1777 -4.258 2.332 -10.848 0.140 1778 1.188 7.778 -5.402 0.329 1779 6.484 13.074 -0.106 0.269 1780 7.328 13.918 0.738 -0.086 1781 2.096 8.686 -4.494 -0.715 1782 -12.888 -6.298 -19.478 -1.492 1783 -1.082 5.508 -7.672 -2.266 1784 -3.791 2.799 -10.381 -2.963 1785 -0.869 5.721 -7.459 -3.539 1786 -7.378 -0.788 -13.968 -4.010 1787 -3.530 3.060 -10.120 -4.452 1788 -2.751 3.839 -9.341 -4.924 1789 -4.391 2.199 -10.981 -5.429 1790 -9.110 -2.520 -15.700 -5.952 1791 -4.742 1.848 -11.332 -6.510 1792 -6.279 0.311 -12.869 -7.084 1793 -9.681 -3.091 -16.271 -7.614 1794 -6.538 0.052 -13.128 -8.074 1795 -7.632 -1.042 -14.222 -8.375 1796 -14.307 -7.717 -20.897 -8.501 1797 -10.853 -4.263 -17.443 -8.428 1798 -4.442 2.148 -11.032 -8.199 1799 -13.284 -6.694 -19.874 -7.892 1800 -1.887 4.703 -8.477 -7.611 1801 -4.161 2.429 -10.751 -7.421 1802 -9.384 -2.794 -15.974 -7.327 1803 -6.973 -0.383 -13.563 -7.307 1804 -7.715 -1.125 -14.305 -7.260 1805 -8.254 -1.664 -14.844 -7.104 1806 -9.748 -3.158 -16.338 -6.804 1807 -8.710 -2.120 -15.300 -6.365 1808 -3.665 2.925 -10.255 -5.849 1809 -4.629 1.961 -11.219 -5.378 1810 -1.685 4.905 -8.275 -5.002 1811 -4.535 2.055 -11.125 -4.756 1812 -3.729 2.861 -10.319 -4.688 1813 -6.249 0.341 -12.839 -4.723 1814 -3.583 3.007 -10.173 -4.777 1815 -3.063 3.527 -9.653 -4.792 1816 -10.838 -4.248 -17.428 -4.722 1817 -7.149 -0.559 -13.739 -4.566 1818 -3.256 3.334 -9.846 -4.366 1819 4.819 11.409 -1.771 -4.187 1820 -5.697 0.893 -12.287 -4.006 1821 -5.999 0.591 -12.589 -3.780 1822 -4.230 2.360 -10.820 -3.393 1823 -9.613 -3.023 -16.203 -2.766 1824 -5.761 0.829 -12.351 -1.925 1825 2.639 9.229 -3.951 -0.945 1826 4.607 11.197 -1.983 0.006 1827 2.528 9.118 -4.062 0.776 1828 4.511 11.101 -2.079 1.268 1829 -0.249 6.341 -6.839 1.529 1830 0.802 7.392 -5.788 1.573 1831 4.399 10.989 -2.191 1.454 1832 -2.819 3.771 -9.409 1.187 1833 0.812 7.402 -5.778 0.708 1834 7.698 14.288 1.108 0.013 1835 3.047 9.637 -3.543 -0.895 1836 -5.798 0.792 -12.388 -1.987 1837 -5.074 1.516 -11.664 -3.137 1838 -5.480 1.110 -12.070 -4.206 1839 -3.819 2.771 -10.409 -5.109 1840 -7.070 -0.480 -13.660 -5.771 1841 -12.893 -6.303 -19.483 -6.132 1842 -3.898 2.692 -10.488 -6.206 1843 -3.762 2.828 -10.352 -6.034 1844 -13.245 -6.655 -19.835 -5.647 1845 -4.456 2.134 -11.046 -5.161 1846 0.272 6.862 -6.318 -4.637 1847 -2.846 3.744 -9.436 -4.165 1848 -4.879 1.711 -11.469 -3.779 1849 -5.283 1.307 -11.873 -3.446 1850 -1.322 5.268 -7.912 -3.153 -1.76 1851 -2.502 4.088 -9.092 -2.855 -1.804 1852 -1.490 5.100 -8.080 -2.531 -1.427 1853 -9.431 -2.841 -16.021 -2.126 -9.834 1854 3.229 9.819 -3.361 -1.699 3.014 1855 -1.407 5.183 -7.997 -1.281 -4.413 1856 -2.776 3.814 -9.366 -0.913 -5.541 1857 2.898 9.488 -3.692 -0.681 3.939 1858 -0.532 6.058 -7.122 -0.631 2.817 -2.119 1859 5.763 12.353 -0.827 -0.730 3.884 -2.574 1860 -6.271 0.319 -12.861 -0.900 -7.261 -3.087 1861 -1.974 4.616 -8.564 -1.080 -12.386 -3.473 1862 -2.031 4.559 -8.621 -1.157 -9.362 -3.609 1863 -2.812 3.778 -9.402 -1.112 0.937 -3.511 1864 0.987 7.577 -5.603 -0.911 0.408 -3.078 1865 -1.835 4.755 -8.425 -0.598 -2.223 -2.489 1866 -4.914 1.676 -11.504 -0.246 -12.606 -1.862 1867 2.897 9.487 -3.693 0.063 1.2 -1.267 1868 6.709 13.299 0.119 0.210 5.239 -0.873 1869 -0.005 6.585 -6.595 0.169 9.931 -0.710 1870 0.277 6.867 -6.313 -0.046 -0.336 -0.769 1871 0.852 7.442 -5.738 -0.420 -16.498 -1.009 1872 -5.580 1.010 -12.170 -0.842 6.141 -1.281 1873 -3.588 3.002 -10.178 -1.347 -6.123 -1.633 1874 3.277 9.867 -3.313 -1.886 -2.504 -2.107 1875 2.532 9.122 -4.058 -2.495 10.592 -2.763 1876 -3.762 2.828 -10.352 -3.127 -2.012 -3.601 1877 -11.750 -5.160 -18.340 -3.722 -7.783 -4.455 1878 -0.523 6.067 -7.113 -4.207 -9.579 -5.193 1879 -11.884 -5.294 -18.474 -4.526 -18.522 -5.521 1880 3.337 9.927 -3.253 -4.694 5.598 -5.346 1881 -8.750 -2.160 -15.340 -4.703 -11.281 -4.739 1882 -2.559 4.031 -9.149 -4.593 -10.46 -3.777 1883 -10.781 -4.191 -17.371 -4.396 -7.269 -2.767 1884 -1.121 5.469 -7.711 -4.108 8.855 -2.029 1885 -2.995 3.595 -9.585 -3.759 16.503 -1.741 1886 -6.085 0.505 -12.675 -3.429 -7.704 -2.004 1887 2.574 9.164 -4.016 -3.171 0.023 -2.723 1888 -3.448 3.142 -10.038 -2.915 -7.441 -3.546 1889 -3.974 2.616 -10.564 -2.684 -9.756 -4.327 1890 -4.116 2.474 -10.706 -2.372 -9.831 -4.722 1891 -6.529 0.061 -13.119 -1.983 -4.765 -4.706 1892 0.035 6.625 -6.555 -1.506 -3.221 -4.318 1893 5.895 12.485 -0.695 -1.003 -1.766 -3.596 1894 -2.726 3.864 -9.316 -0.474 -3.97 -2.624 1895 -3.939 2.651 -10.529 0.058 -12.256 -1.453 1896 0.343 6.933 -6.247 0.559 10.342 -0.199 1897 0.808 7.398 -5.782 0.945 -6.254 0.984 1898 2.559 9.149 -4.031 1.122 4.844 1.880 1899 8.685 15.275 2.095 0.969 11.118 2.308 1900 4.696 11.286 -1.894 0.498 5.361 2.187 1901 -0.366 6.224 -6.956 -0.255 12.881 1.549 1902 -6.404 0.186 -12.994 -1.144 -2.241 0.631 1903 -6.418 0.172 -13.008 -1.973 -17.301 -0.256 1904 2.608 9.198 -3.982 -2.671 1.032 -0.960 1905 -6.828 -0.238 -13.418 -3.147 -1.403 -1.352 1906 -1.438 5.152 -8.028 -3.363 -1.13 -1.405 1907 -9.820 -3.230 -16.410 -3.328 0.722 -1.225 1908 -2.103 4.487 -8.693 -3.098 3.152 -0.841 1909 -4.141 2.449 -10.731 -2.696 -11.764 -0.277 1910 -2.870 3.720 -9.460 -2.261 -5.262 0.357 1911 3.725 10.315 -2.865 -1.875 12.761 0.965 1912 -2.829 3.761 -9.419 -1.668 -2.786 1.395 1913 1.356 7.946 -5.234 -1.646 14.835 1.462 1914 -0.170 6.420 -6.760 -1.760 1.188 1.219 1915 -2.531 4.059 -9.121 -1.945 -2.723 0.727 1916 -8.818 -2.228 -15.408 -2.109 -4.151 0.104 1917 -0.155 6.435 -6.745 -2.232 -1.7 -0.516 1918 -4.432 2.158 -11.022 -2.302 0.205 -1.114 1919 4.348 10.938 -2.242 -2.390 -1.565 -1.797 1920 -4.171 2.419 -10.761 -2.532 4.112 -2.607 1921 -0.361 6.229 -6.951 -2.667 -1.794 -3.420 1922 -7.767 -1.177 -14.357 -2.830 -5.217 -4.261 1923 -3.759 2.831 -10.349 -2.960 -12.344 -4.923 1924 -5.201 1.389 -11.791 -3.087 -14.586 -5.332 1925 1.631 8.221 -4.959 -3.197 0.345 -5.521 1926 2.385 8.975 -4.205 -3.331 -0.269 -5.570 1927 -6.445 0.145 -13.035 -3.365 -6.141 -5.527 1928 -10.837 -4.247 -17.427 -3.250 -8.417 -5.423 1929 -1.469 5.121 -8.059 -2.842 0.308 -5.180 1930 -8.122 -1.532 -14.712 -2.131 -13.132 -4.705 1931 0.198 6.788 -6.392 -1.172 -11.771 -3.943 1932 -2.092 4.498 -8.682 -0.153 2.017 -2.916 1933 6.627 13.217 0.037 0.764 0.395 -1.724 1934 2.491 9.081 -4.099 1.379 -2.082 -0.523 1935 9.187 15.777 2.597 1.644 2.872 0.551 1936 0.464 7.054 -6.126 1.599 -2.002 1.367 1937 -0.595 5.995 -7.185 1.330 8.28 1.760 1938 2.069 8.659 -4.521 0.979 6.518 1.639 1939 -1.502 5.088 -8.092 0.786 6.927 1.121 1940 -4.284 2.306 -10.874 0.757 0.299 0.247 1941 1.138 7.728 -5.452 0.975 -3.933 -0.677 1942 -1.021 5.569 -7.611 1.286 -4.652 -1.437 1943 5.070 11.660 -1.520 1.628 -10.132 -1.791 1944 7.540 14.130 0.950 1.846 -1.629 -1.704 1945 1.458 8.048 -5.132 1.875 -3.545 -1.275 1946 -3.409 3.181 -9.999 1.661 -3.456 -0.774 1947 9.998 16.588 3.408 1.275 11.798 -0.303 1948 -3.842 2.748 -10.432 0.717 -3.582 -0.192 1949 6.206 12.796 -0.384 0.130 12.962 -0.413 1950 -7.753 -1.163 -14.343 -0.432 -9.741 -0.946 1951 -1.903 4.687 -8.493 -0.850 -1.554 -1.563 1952 -0.607 5.983 -7.197 -1.154 -0.88 -2.137 1953 -2.745 3.845 -9.335 -1.351 -7.709 -2.543 1954 -4.072 2.518 -10.662 -1.490 -16.208 -2.731 1955 10.841 17.431 4.251 -1.641 19.429 -2.768 1956 -11.199 -4.609 -17.789 -1.873 -11.856 -2.751 1957 -0.976 5.614 -7.566 -2.164 -0.426 -2.732 1958 -4.385 2.205 -10.975 -2.541 -9.33 -2.787 1959 4.734 11.324 -1.856 -2.915 7.78 -2.816 1960 -4.799 1.791 -11.389 -3.258 -7.552 -2.796 1961 -6.894 -0.304 -13.484 -3.478 -4.833 -2.631 1962 -7.628 -1.038 -14.218 -3.476 -3.742 -2.256 1963 -5.034 1.556 -11.624 -3.182 -3.418 -1.544 1964 -2.134 4.456 -8.724 -2.653 1.798 -0.484 1965 -5.147 1.443 -11.737 -1.897 -8.143 0.980 1966 0.919 7.509 -5.671 -1.149 -1.362 2.579 1967 3.924 10.514 -2.666 -0.414 4.517 4.201 1968 5.144 11.734 -1.446 0.242 19.844 5.582 1969 -3.617 2.973 -10.207 15.78 6.581 1970 -5.586 1.004 -12.176 -2.431 7.130 1971 3.780 10.370 -2.810 4.336 7.311 1972 4.916 11.506 -1.674 18.771 7.268 1973 8.484 15.074 1.894 5.56 7.169 1974 -2.811 3.779 -9.401 -6.813 7.086 1975 9.842 16.432 3.252 7.595 6.999 1976 10.233 16.823 3.643 19.657 6.857 1977 7.195 6.562 1978 7.067 6.210 1979 1.733 5.853 1980 -2.099 5.430 1981 8.954 5.007 1982 4.626 4.566 1983 11.036 3.988 1984 9.469 3.162 1985 -7.293 2.235 1986 2.936 1.376 1987 3.099 0.668 1988 -14.381 0.240 1989 2.713 0.126 1990 8.437 0.200 1991 2.99 0.518 1992 -12.797 0.994 1993 1.518 1.558 1994 6.136 2.146 1995 2.588 2.537 1996 9.422 2.655 1997 14.762 2.542 1998 -10.947 1999 -0.793 2000 0.705 2001 -2.097 2002 8.133 2003 3.841 2004 -1.955 2005 3.551 2006 9.927 2007 -10.390 2008 -12.655 2009 -5.591