This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Web of Science (3) Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Andrade, C. Articles by Ramos, A.M. Search for Related Content GeoRef GeoRef Citation Social Bookmarking                         What's this?

Comparing historic records of storm frequency and the North Atlantic Oscillation (NAO) chronology for the Azores region

Centro de Geologia, Departamento de Geologia, Faculdade de Ciências, Universidade de Lisboa, Bloco C 6, 3 Piso, Campo Grande, 1749-016 Lisboa, Portugal, candrade{at}fc.ul.pt

R.M. Trigo

University of Lisbon, CGUL, IDL, C8, Piso 6, Campo Grande, 1749-016, Lisboa, Portugal, Universidade Lusófona, Departamento de Engenharias, Lisboa, Portugal

M.C. Freitas

Centro de Geologia, Departamento de Geologia, Faculdade de Ciências, Universidade de Lisboa, Bloco C 6, 3 Piso, Campo Grande, 1749-016 Lisboa, Portugal

M.C. Gallego

Departamento de Física, Facultad de Ciencias, Universidad de Extremadura, Avda. de Elvas s/n, 06071 Badajoz, Spain

P. Borges

Departamento de Geociências da Universidade dos Açores. Rua da Me de Deus, Apartado 1422, 9501-801 Ponta Delgada Codex, Ponta Delgada, Açores, Portugal

A.M. Ramos

University of Lisbon, CGUL, IDL, C8, Piso 6, Campo Grande, 1749-016, Lisboa, Portugal

The storminess of the Azores region was investigated using newspaper records from AD 1836 onwards. The information obtained was rank-ordered for intensity and the time series of storm frequency analysed for interannual- to century-scale variability. The documentary data set was validated by comparison with objective cyclones intensity for the period AD 1958—2000. Results indicate that four periods of contrasting storm frequency are present (AD 1836—1870, 1870—1920, 1920—1940 and 1940—1998). The average storm lasts for 2.3 days and the average secular storm frequency is 3.1 storms/yr. Low intensity events occur four times every five years whereas an extreme storm occurs on average once every seven years. The documentary index of storminess is highly variable at different timescales, which is consistent with other studies of storminess in the North Atlantic. Nevertheless, an objective comparison between late nineteenth- and late twentieth-century storm frequency does not reveal a significant difference. Between AD 1865 and the late twentieth century the winter NAO and storminess indices show a statistically significant anti-correlation pattern at the monthly and seasonal scales. In the late nineteenth century and between AD 1950 and 1970 the NAO index was low and the storminess index high, whilst the opposite occurred from the early twentieth century until the middle 1950s; since AD 1970 both indexes reveal positive trends and are predominantly positive. The NAO mode of circulation is partially responsible for the storminess spatial pattern and temporal distribution over the Azores region since AD 1865 and for about a century, however this relation appears to have weakened since the 1960s.

Key Words: Storminess • documentary record • historical evidence • North Atlantic Oscillation • NAO • Azores • storm-tracking.

The Holocene, Vol. 18, No. 5, 745-754 (2008)
DOI: 10.1177/0959683608091794


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?