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Leila M. V. Carvalho and Charles Jones

1. Introduction The presence of a monsoonal type of circulation involving intense convective activity and heavy precipitation is the dominant climatic feature in the tropical Americas during the respective summer seasons. The North American monsoon system (NAMS) and the South American monsoon system (SAMS) are often interpreted as the two extremes of the seasonal cycle of heat, moisture transport, and precipitation over the Americas ( Vera et al. 2006 ). The SAMS and NAMS seasonal cycles are

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Zeng-Zhen Hu and Bohua Huang

moisture transport into the North American continent and cause convergence or divergence, leading to dry or wet spells over specific geographic areas ( Mo et al. 1997 ). Conceptually, these circulation anomalies can be further decomposed into internal variability and externally forced components. The former originates from dynamical evolution within the atmosphere, which is usually chaotic in nature and becomes unpredictable beyond a month ( Shukla 1981 ). The latter, however, is usually the forced

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James Foster, Manfred Owe, and Albert Rango

460 JOURNAL OF CLIMATE AND APPLIED METEOROLOGY VOLUME22Snow Cover and Temperature Relationships in North America and Eurasia JAMES FOSTER, MANFRED OWE AND ALBERT RANGONASA Goddard Space Flight Center, Earth Survey Applications Division, Hydrological Sciences Branch, Greenbelt, MD 20771(Manuscript received 28 June 1982, in final form 24 November 1982)ABSTRACT In this study the snow cover

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Robert S. Gaza and Lance F. Bosart

314 WEATHER AND FORECASTING VOLUME5Trough-Merger Characteristics over North America ROBERT S. GAZA* AND LANCE F. BOSARTDepartment of Atmospheric Science, State University of New York at Albany, Albany, New York(Manuscript ~:eived 20 October 1989, in final form January 1990)ABSTRACT Split flow, defined by the presence of two separate westerly airstreams in the mid- and upper troposphere, iscommon in middle

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Mathew Barlow, Sumant Nigam, and Ernesto H. Berbery

referred to as the North American monsoon system. The summertime precipitation over North America exhibits a considerable range of magnitudes, as evident from Fig. 1a , which displays the observed mean July precipitation for the 1979–85 period. Although primarily convective in nature even in the more northerly latitudes of the contiguous United States ( Heideman and Fritsch 1988 ), the precipitation is associated with a diverse array of processes—for example, a monsoonal land sea regime along the U

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Honghai Zhang and Thomas L. Delworth

2013) ; Hoerling et al. 2011 ; Xie et al. 2015 ; Sarojini et al. 2016 ]. The important role of internal climate variability on relatively small spatiotemporal scales has recently been highlighted in a number of studies. For example, Deser et al. (2012 , 2014) analyzed North American climate projections over 2010–60 in two large ensembles of climate change simulations conducted with two climate models: the National Center for Atmospheric Research CCSM3 (40 simulations) and the Max Planck

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Katherine M. Willingham, Elizabeth J. Thompson, Kenneth W. Howard, and Charles L. Dempsey

1. Introduction During the North American monsoon season, convective storms in the southwestern U.S. Sonoran Desert produce damaging microbursts (e.g., Vasiloff and Howard 2009 ; Fig. 1 ). Severe winds from microbursts can threaten aviation operations, damage property, and interrupt communications, transportation, and electrical power transmission. Because of rapid urban expansion and the rising population density of central Arizona, specifically in the Phoenix metropolitan area, the

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Yan Ge and Gavin Gong

North America have been used to discern statistical associations between snow depth and climate over selected regions. Most of these works were based on the observations at western part of the United States and demonstrated the effects of precipitation and temperature variability on snow depth or snow water equivalent ( Cayan et al. 1996 ; McCabe and Dettinger 2002 ; Jin et al. 2006 ; Mote 2006 ). Serreze et al. (1998) and Hartley and Keables (1998) associated snowfall regimes over the

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M. A. Ben Alaya, F. Zwiers, and X. Zhang

distribution is fitted are indeed max-stable, there is then a question as to whether the fitted distribution can be used to extrapolate beyond available samples of extremes. This paper uses a large ensemble of historical simulations from the Canadian Regional Climate Model (CanRCM4) over North America to assess whether simulated extreme daily and subdaily precipitation amounts simulated by that model can be well described by a max-stable distribution (i.e., the GEV distribution), and to explore the

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Michael Wehner, David R. Easterling, Jay H. Lawrimore, Richard R. Heim Jr., Russell S. Vose, and Benjamin D. Santer

agriculture. The Palmer drought severity index (PDSI) is a widely recognized measure of droughts extending several months or more ( Heim 2002 ). In this paper, we examine the ability of the climate models used in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) to reproduce observed PDSI statistics over North America ( Solomon et al. 2007 ). We rank the models’ performance by a variety of measures, and explore whether performance in simulating current climate is

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