Premium
On the development of strong ridge episodes over the eastern North Atlantic
Author(s) -
Santos João A.,
Pinto Joaquim G.,
Ulbrich Uwe
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl039086
Subject(s) - anticyclone , geopotential height , rossby wave , ridge , geology , climatology , anomaly (physics) , geopotential , troposphere , stratosphere , latitude , jet stream , jet (fluid) , geography , meteorology , geodesy , paleontology , precipitation , physics , condensed matter physics , thermodynamics
The occurrence of strong and persistent mid‐latitude anticyclonic ridges over the Eastern North Atlantic is a major contributor to the occurrence of severe winter droughts over Western Iberia. We analyze the development of strong and persistent ridge episodes within 40–50°N; 40°W–5°E, which are defined as 300 hPa geopotential height anomalies above 50 gpm that persist for at least 10 consecutive days. Results suggest that the generation and maintenance of these episodes, with positive stratospheric geopotential anomalies over the North American continent and the adjacent North Pacific, are associated with an intensified polar jet. Such positive anomalies tend to detach from the main stratospheric anomaly and propagate eastwards and downwards as Rossby tropospheric waves. Furthermore, the Eastern North Atlantic ridge is generated and repeatedly reinforced until the stratospheric anomaly dissipates. Results also show evidence for waves breaking anticyclonically during the episodes, which is dynamically coherent with their persistency and quasi‐stationarity.