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  • Waves, oceanic x
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Lixia Zhang and Tianjun Zhou

). The positive SST anomalies and associated precipitation anomalies over the Indian Ocean can warm the total troposphere and induce the upper-level circulation changes. Tropospheric warming emerges as a Matsuno–Gill ( Matsuno 1966 ; Gill 1980 ) pattern with the heating anchored over the tropical Indian Ocean and exhibits a wedge penetrating into the WNP ( Fig. 5c ). Westerly winds dominate the equatorial Indo–western Pacific region, as the high-level Kelvin wave response of the Matsuno–Gill pattern

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Siegfried D. Schubert, Hailan Wang, Randal D. Koster, Max J. Suarez, and Pavel Ya. Groisman

of the oceans and various air masses (tropical, subtropical, and polar) across the continent and the arrangement of Eurasia’s major mountain chains. The recent extreme heat waves and droughts of 2003 (Europe) and 2010 (Russia) have highlighted the urgency of understanding better their causes and whether or not they are a manifestation of a warming world (e.g., Dole et al. 2011 ; Trenberth and Fasullo 2012 ; Otto et al. 2012 ). While there is agreement on many aspects of such extreme events

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Siegfried D. Schubert, Ronald E. Stewart, Hailan Wang, Mathew Barlow, Ernesto H. Berbery, Wenju Cai, Martin P. Hoerling, Krishna K. Kanikicharla, Randal D. Koster, Bradfield Lyon, Annarita Mariotti, Carlos R. Mechoso, Omar V. Müller, Belen Rodriguez-Fonseca, Richard Seager, Sonia I. Seneviratne, Lixia Zhang, and Tianjun Zhou

. Anomalous warming of the southern tropical Atlantic enhances ascent over the Gulf of Guinea and descent over the Sahel. A warming in the Pacific and Indian Oceans generates equatorial Rossby waves that contribute to subsidence over the Sahel and thus to reduce regional precipitation. In addition, Mediterranean warm events are linked to increased moisture flux convergence over the Sahel. Decadal SST variability and global warming are also relevant to Sahelian drought. In recent decades the Sahel has been

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Richard Seager and Martin Hoerling

observed and idealized sea surface temperatures (SSTs). These were used to test hypotheses of oceanic forcing of drought-inducing atmospheric circulation anomalies. Links between North American precipitation variability and the El Niño–Southern Oscillation (ENSO), with, in its El Niño phase, a tendency to increased winter precipitation across southern North America, had begun to be noticed in the 1970s and early 1980s (see Rasmusson and Wallace 1983 ) and explained in terms of Rossby wave propagation

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Belen Rodríguez-Fonseca, Elsa Mohino, Carlos R. Mechoso, Cyril Caminade, Michela Biasutti, Marco Gaetani, J. Garcia-Serrano, Edward K. Vizy, Kerry Cook, Yongkang Xue, Irene Polo, Teresa Losada, Leonard Druyan, Bernard Fontaine, Juergen Bader, Francisco J. Doblas-Reyes, Lisa Goddard, Serge Janicot, Alberto Arribas, William Lau, Andrew Colman, M. Vellinga, David P. Rowell, Fred Kucharski, and Aurore Voldoire

Indian Ocean acts through changes in the large-scale gradient in SSTs from the west Pacific to the Indian Ocean. AGCM experiments showed that these changes lead to a stationary equatorial Rossby wave response over the Indian Ocean, causing anomalous subsidence over the Sahel. e. Modulation of the interannual variability by lower-frequency variations Studies performed in the last decades have argued that the impact of SST anomalies in some basins appear to be different depending on the decades

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Wenju Cai, Ariaan Purich, Tim Cowan, Peter van Rensch, and Evan Weller

Pacific–South America (PSA)-equivalent wave train patterns ( section 3b ). Often El Niño is associated with a positive IOD ( Ummenhofer et al. 2011 ), during which SSTs off the Sumatra–Java coast are cooler than normal, but warmer than normal over the western tropical Indian Ocean ( Saji et al. 1999 ). Over 1950–2009, this pathway appears to operate not only during spring, but also winter, with associated rainfall anomalies seen along the inland eastern region of Australia, but not along the eastern

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Mathew Barlow, Benjamin Zaitchik, Shlomit Paz, Emily Black, Jason Evans, and Andrew Hoell

forecasts of the Amu Dar’ya and Syr Dar’ya. The link to tropical oceans suggests both that model forecast skill may improve with model improvements and that the state of the tropical oceans, current and predicted, could be used directly to forecast seasonal precipitation in the region. Accurate representation of the Asian jet structure is a key issue for models because of the importance of jet interaction with the stationary wave response to tropical forcing. Snowmelt, which in some parts of the region

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