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Fuyao Wang, Zhengyu Liu, and Michael Notaro

modes have not been well studied. ENSO is considered the most prominent source of climate interannual variability, and its impact on North American climate has been recognized for decades ( Ropelewski and Halpert 1986 , 1987 ; Ting and Wang 1997 ; Zhang et al. 2011 ). In winter, past studies generally agree that, during the warm phase of ENSO, the air is warmer than normal stretching from northwestern North America to eastern Canada, colder than normal in the southern and southeastern U

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Katrina Grantz, Balaji Rajagopalan, Martyn Clark, and Edith Zagona

1. Introduction and background The North American monsoon system (NAMS) is the large-scale atmospheric circulation system that drives the dramatic increase in rainfall experienced in the desert southwest United States and northwestern Mexico during the summer months of July, August, and September. These summer thunderstorms typically begin in early July and last until mid-September and can account for as much as 50%–70% of the annual precipitation in the arid region ( Carleton et al. 1990

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Yan Ge, Gavin Gong, and Allan Frei

1. Introduction Various prominent teleconnection patterns, such as El Niño–Southern Oscillation (ENSO), Pacific decadal oscillation (PDO), North Atlantic Oscillation (NAO), and Pacific–North American (PNA), are known to impact climate conditions over North America (NA), most notably during the Northern Hemisphere (NH) winter. These recurrent atmospheric circulation patterns are associated with variations in the intensity and location of the polar jet stream, the subtropical jet stream, or

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Wayne Higgins and David Gochis

1. The NAME Process Study The North American Monsoon Experiment (NAME) is an internationally coordinated process study aimed at determining the sources and limits of predictability of warm season precipitation over North America. The NAME program is jointly sponsored by the Climate Variability and Predictability (CLIVAR) and Global Energy and Water Cycle Experiment (GEWEX) interdisciplinary research efforts. NAME seeks improved understanding of the key physical processes that must be

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Alvaro Avila-Diaz, David H. Bromwich, Aaron B. Wilson, Flavio Justino, and Sheng-Hung Wang

average ( Walsh et al. 2017 ), is needed. Accurate representation of extremes across the Arctic is essential to the development of public policies, proper management of hydrological resources, and mitigation of impacts from human activity on the environment, as future projections over North America indicate a significant decrease in cold extremes and increase in warm extremes by the end of the twenty-first century ( Schoof and Robeson 2016 ; Lader et al. 2017 ; Sheridan and Lee 2018 ; Wazneh et al

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Toby R. Ault and Scott St. George

1. Introduction Recent studies have suggested that the risk of drought over North America changes at time scales of one to several decades, and that these changes are linked to variations in ocean temperatures. Enfield et al. (2001) found that summer rainfall in the continental United States is correlated with the Atlantic multidecadal oscillation (AMO), with less rain falling during the warm phase of the AMO. Similarly, McCabe et al. (2004) demonstrated that multidecadal drought frequency

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Emily J. Becker, Ernesto Hugo Berbery, and R. Wayne Higgins

North America (e.g., Ropelewski and Halpert 1986 , 1996 ; Kiladis and Diaz 1989 ; Mo and Higgins 1998 ), also affects the character of daily precipitation. According to Schubert et al. (2005) , La Niña years tend to produce considerably fewer extreme storms than El Niño years along the Gulf and East Coasts. Higgins et al. (2007) found that during winter the Southwest averages up to 15% more days with measurable (>1 mm) precipitation per season during El Niño phases, compared to La Niña. On

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Sally Langford, Samantha Stevenson, and David Noone

1. Introduction Southwestern North America is projected to undergo drying in the twenty-first century ( Seager et al. 2007 ; Cayan et al. 2010 ; Christensen and Lettenmaier 2007 ), potentially increasing the frequency of occurrence and duration of drought-like conditions in the region. Climate records derived from tree core measurements (e.g., Stahle et al. 2007 ; Cook et al. 2004 ; Woodhouse et al. 2006 ) or vegetation growth in lake beds (e.g., Stine 1994 ) from the past millennia

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Celine Herweijer, Richard Seager, Edward R. Cook, and Julien Emile-Geay

1. Introduction Modern-day North America, especially the water-thirsty West, needs little reminder of the cost of drought: “water shortages” and “wildfires” are familiar midsummer season headlines, and tales of devastation from the 1930s Dust Bowl and 1950s Southwestern droughts are far from forgotten. As recently as 1998, widespread drought conditions returned to the American West and Plains, and another multiyear drought event commenced, persisting in the Northern Plains and western Canda

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Stefan Sobolowski, Gavin Gong, and Mingfang Ting

Northern Hemisphere from mid- to high latitudes. Because of this spatiotemporal variation and the striking geographical differences between the North American and Eurasian landmasses, the influence of snow on climate and the physical pathways through which this influence is expressed is still an area of ongoing research. In particular, questions regarding large-scale dynamic responses and their corresponding mechanisms abound. Evidence for physically based snow climate teleconnections is more abundant

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