Extension to the North Atlantic oscillation using early instrumental pressure observations from Gibraltar and south‐west Iceland

Early instrumental pressure measurements from Gibraltar and the Reykjavik area of Iceland have been used to extend to 1821 the homogeneous pressure series at the two locations In winter the two sites are located close to the centres of action that comprise the North Atlantic Oscillation (NAO). The extended 'winter half-year' record of the NAO enables recent changes in the record to be placed in the context of the period 1823-1996 The period since the early 1970s is the most prolonged positive phase of the oscillation and the late 1980s and early 1990s is the period with the highest values (strongest westerlies) The winter of 1995-1996 marked a dramatic switch in the index, with the change from 1994-1995 being the greatest change recorded from one year to the next since the series began in 1923. (The extended Gibraltar and Reykjavik monthly pressures and the NAO series can be found on the Climatic Research Unit home page. www.cru.uea-ac.uk.

[1]  H. Lamb,et al.  Secular variations of the atmospheric circulation since 1750 , 1966 .

[2]  H. Loon,et al.  The Seesaw in Winter Temperatures between Greenland and Northern Europe. Part I: General Description , 1978 .

[3]  J. Wallace,et al.  Teleconnections in the Geopotential Height Field during the Northern Hemisphere Winter , 1981 .

[4]  J. Rogers.  The Association between the North Atlantic Oscillation and the Southern Oscillation in the Northern Hemisphere , 1984 .

[5]  J. Rogers.  Atmospheric Circulation Changes Associated with the Warming over the Northern North Atlantic in the 1920s , 1985 .

[6]  P. Jones,et al.  An Extension of the TahitiDarwin Southern Oscillation Index , 1987 .

[7]  A. Barnston,et al.  Classification, seasonality and persistence of low-frequency atmospheric circulation patterns , 1987 .

[8]  D. Wheeler,et al.  Rainfall characteristics of Mainland Europe's most southerly stations , 1992 .

[9]  D. Wheeler.  Early instrumental weather data from Cadiz: A study of late eighteenth and early nineteenth century records , 1995 .

[10]  J. Hurrell.  Decadal Trends in the North Atlantic Oscillation: Regional Temperatures and Precipitation , 1995, Science.

[11]  E. Mosley‐Thompson,et al.  Atlantic Arctic cyclones and the mild Siberian winters of the 1980s , 1995 .

[12]  J. Hurrell.  Influence of variations in extratropical wintertime teleconnections on northern hemisphere temperature , 1996 .

[13]  P. Jones,et al.  PRECIPITATION IN THE BRITISH ISLES: AN ANALYSIS OF AREA‐AVERAGE DATA UPDATED TO 1995 , 1997 .

[14]  P. Jones,et al.  Pre-1866 extensions of the Southern oscillation index using early Indonesian and Tahitian meteorological readings , 1998 .