Low-frequency climate variability in the Atlantic basin during the 20th century

Extract of ATMOSPHERIC SCIENCE LETTERS Atmos. Sci. Let. (2010) Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/asl.265

Received: 20 May 2009 Revised: 17 January 2010 Accepted: 2 February 2010

Y. M. Tourre,1,2 S. Paz,3* Y. Kushnir2 and W. B. White4 1METEO-France, Toulouse, France 2LDEO of Columbia University, Palisades, NY, USA 3Department of Geography and Environmental Studies, University of Haifa, Haifa, Israel 4Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA

Abstract From joint sea surface temperature/sea level pressure (SST/SLP) EOF analyses, lowfrequency variability modes are compared. The multi-decadal oscillation (MDO) changed phases twice during the 20th century, with its north Atlantic SST patterns resembling the Atlantic multi-decadal oscillation (AMO). The quasi-decadal oscillation (QDO) SST patterns displayed a double tripole configuration over the entire Atlantic basin, leading to tropical inter-hemispheric out-of-phase relationship. From the mid-1960s onward, while SST anomalies were negative to the north (negative phases of MDO/AMO), the Sahelian drought persisted with a weaker hurricane power dissipation index (PDI). During that period, the QDO modulated the intensity of the Sahelian drought. Copyright  2010 Royal Meteorological Society Keywords: multi-decadal oscillation; quasi-decadal oscillation; Sahelian drought; power dissipation index