Monthly values of the North Atlantic Oscillation Index from 1821 to 2000, supplement to: Jones, Philip D; Jonsson, T; Wheeler, Dennis A (1997): Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland. International Journal of Climatology, 17(13), 1433-1450

• Main Authors: Jones, Philip D, Jonsson, T, Wheeler, Dennis A
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 1997
• Subjects: DATE/TIME; North Atlantic Ocean Index; Calculation; Calculated; Iceland; North Atlantic; North Atlantic oscillation
• Online Access: https://dx.doi.org/10.1594/pangaea.56559; https://doi.pangaea.de/10.1594/PANGAEA.56559

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 1823. (The extended Gibraltar and Reykjavik monthly pressures and the NAO series can be found on the Climatic Research Unit home page, http://www.cru.uea.ac.uk/). : The North Atlantic Oscillation (NAO) is defined as the normalized pressure difference between a station on the Azores and one on Iceland. NOA is one of the major modes of variability of the Northern Hemisphere atmosphere. It is particularly important in winter, when it exerts a strong control on the climate of the Northern Hemisphere. It is also the season that exhibits the strongest interdecadal variability. For winter, the difference between the normalised sea level pressure over Gibraltar and the normalised sea level pressure over Southwest Iceland is a useful index of the strength of the NAO. Jones et al. (1997) used early instrumental data to extend this index back to 1823.