{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,8]],"date-time":"2025-11-08T17:10:18Z","timestamp":1762621818924,"version":"3.41.2"},"reference-count":17,"publisher":"American Geophysical Union (AGU)","issue":"17","license":[{"start":{"date-parts":[[2009,9,2]],"date-time":"2009-09-02T00:00:00Z","timestamp":1251849600000},"content-version":"vor","delay-in-days":1,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Geophysical Research Letters"],"published-print":{"date-parts":[[2009,9]]},"abstract":"<jats:p>The occurrence of strong and persistent mid\u2010latitude 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\u201350\u00b0N; 40\u00b0W\u20135\u00b0E, 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\u2010stationarity.<\/jats:p>","DOI":"10.1029\/2009gl039086","type":"journal-article","created":{"date-parts":[[2009,9,1]],"date-time":"2009-09-01T20:02:03Z","timestamp":1251835323000},"source":"Crossref","is-referenced-by-count":36,"title":["On the development of strong ridge episodes over the eastern North Atlantic"],"prefix":"10.1029","volume":"36","author":[{"given":"Jo\u00e3o A.","family":"Santos","sequence":"first","affiliation":[{"name":"CITAB, Department of Physics University of Tras\u2010os\u2010Montes and Alto Douro  Vila Real Portugal"}]},{"given":"Joaquim G.","family":"Pinto","sequence":"additional","affiliation":[{"name":"Institute for Geophysics and Meteorology University of Cologne  Cologne Germany"}]},{"given":"Uwe","family":"Ulbrich","sequence":"additional","affiliation":[{"name":"Institute for Meteorology Freie Universit\u00e4t Berlin  Berlin Germany"}]}],"member":"13","published-online":{"date-parts":[[2009,9,2]]},"reference":[{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.1063315"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1175\/1520\u20100469(2004)061<0121:SVOTNA>2.0.CO;2"},{"key":"e_1_2_6_4_1","doi-asserted-by":"publisher","DOI":"10.1029\/2000JD000214"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1256\/qj.02.76"},{"key":"e_1_2_6_6_1","doi-asserted-by":"publisher","DOI":"10.1175\/JHM578.1"},{"key":"e_1_2_6_7_1","doi-asserted-by":"publisher","DOI":"10.1029\/2006GL025734"},{"key":"e_1_2_6_8_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.269.5224.676"},{"key":"e_1_2_6_9_1","doi-asserted-by":"publisher","DOI":"10.1175\/1520\u20100477(2001)082<0247:TNNYRM>2.3.CO;2"},{"key":"e_1_2_6_10_1","doi-asserted-by":"publisher","DOI":"10.1175\/2009JCLI2750.1"},{"key":"e_1_2_6_11_1","doi-asserted-by":"publisher","DOI":"10.1002\/joc.1425"},{"key":"e_1_2_6_12_1","doi-asserted-by":"publisher","DOI":"10.1002\/joc.1818"},{"key":"e_1_2_6_13_1","doi-asserted-by":"publisher","DOI":"10.1038\/nature02300"},{"key":"e_1_2_6_14_1","doi-asserted-by":"publisher","DOI":"10.1038\/nature03089"},{"key":"e_1_2_6_15_1","first-page":"235","volume-title":"Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change","author":"Trenberth K. 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