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Roger M. Wakimoto and Hanne V. Murphey

of moisture have been difficult to collect in field studies. Moreover, variations of moisture over distances of only a few kilometers, as suggested by the modeling studies, have been shown to commonly occur within the convective boundary layer (e.g., Weckwerth et al. 1996 ; Weckwerth 2000 ; Murphey et al. 2006 ). The present study focuses on a dryline that developed on 22 May 2002 during the International H 2 O Project (IHOP; Weckwerth et al. 2004 ). The dryline is a convergence line that

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Zachary F. Johnson and Nathan M. Hitchens

1. Introduction The dryline, a transition zone that separates dry air from moist air, is an important meteorological phenomenon in the Great Plains of the United States ( Fujita 1958 ) and is a focus for research because of its effect on severe and fire weather forecasting in that region. Many violent tornadoes have occurred as a result of dryline convection; therefore, an emphasis of past research has been on dryline dynamics. However, interactions between the land and atmosphere, as well as

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David M. Schultz, Christopher C. Weiss, and Paul M. Hoffman

1. Introduction The dryline is an airstream boundary (e.g., Cohen and Kreitzberg 1997 ; Cohen and Schultz 2005 ) separating moist air originating over the Gulf of Mexico from dry air originating over the southwestern United States and high plateau of Mexico (e.g., Fujita 1958 ; Beebe 1958 ; Rhea 1966 ; Schaefer 1974a , 1986 ). The dryline typically forms along the high plains in the spring months and is a frequent site of convection initiation. The details of the processes that control

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Bart Geerts

1. Introduction The dryline is a well-defined atmospheric boundary observed over the southern Great Plains, between hot dry air to the west and air of maritime tropical (mT) origin to the east. To a first order, the dryline can be viewed as the intersection of the top of a level, capped boundary layer (BL) containing the mT air mass and the sloping terrain east of the Rocky Mountains (e.g., Schaefer 1974 ). The dryline has clear diurnal characteristics and becomes more defined during the

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Sarah J. Arnup and Michael J. Reeder

1. Introduction A front is the sloping interface between air masses of different origins and with different thermodynamic properties. Examples in the Australian region include the summertime cool changes that sweep across southern Australia, their subtropical extensions that penetrate into the low latitudes in the dry season, and the sharp sea breezes common to most of the coastline [see the review by Reeder and Smith (1998) and the references therein]. A dryline is characterized by a large

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Benjamin D. Sipprell and Bart Geerts

1. Introduction The formation of drylines is a well known yet still poorly understood factor in the initiation of deep convection [referred to as convection initiation (CI)]. Notwithstanding much observational research ( Mahrt 1977 ; McCarthy and Koch 1982 ; Koch and McCarthy 1982 ; Wilson and Schreiber 1986 ; Parsons et al. 1991 ; Lee et al. 1991 ; Wilson et al. 1992 ; Hane et al. 1993 ; Ziegler and Hane 1993 ; Fankhauser et al. 1995 ; Hane et al. 1997 ; Crawford and Bluestein 1997

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Michael S. Buban, Conrad L. Ziegler, Erik N. Rasmussen, and Yvette P. Richardson

1. Introduction Surface boundaries such as fronts (e.g., Carbone 1982 ; Nielsen and Neilley 1990 ), sea breezes (e.g., Laird et al. 1995 ; Kingsmill 1995 ), and thunderstorm outflows (e.g., Wakimoto 1982 ; Mahoney 1988 ) play an important role in the initiation of deep convection, and thus have been extensively studied. The dryline has also become a subject of increasing interest due to its frequent association with convection initiation (CI) and subsequent development of severe weather

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Stanley B. Trier, Glen S. Romine, David A. Ahijevych, Robert J. Trapp, Russ S. Schumacher, Michael C. Coniglio, and David J. Stensrud

1. Introduction Large longitudinal contrasts in lower-tropospheric water vapor occur climatologically across the southern Great Plains (SGP) of the United States. Diurnally driven processes in spring and early summer often result in localized gradients of water vapor mixing ratio ( q υ ), referred to as drylines (e.g., McGuire 1962 ). SGP drylines are of meteorological interest because they often serve as a focus for severe convection ( Rhea 1966 ). Incipient convection that forms along or

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Rebecca S. Duell and Matthew S. Van Den Broeke

1. Introduction The dryline is an airmass boundary marked by a strong moisture gradient. In the United States, the dryline typically sets up meridionally over the Great Plains during spring and marks the boundary between hot, dry air from the Mexican Plateau and warm, moist air originating over the Gulf of Mexico. The dryline tends to be a zone of enhanced convergence, which makes it a focal point for convection initiation (e.g., Rhea 1966 ; Schaefer 1974 , 1986 ; Hane et al. 1997 ; Atkins

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Hernán Bechis, Paola Salio, and Juan José Ruiz

1. Introduction In a broad sense, the literature defines drylines as airmass boundaries characterized by a sharp horizontal contrast in the low-level humidity fields ( Owen 1966 ; Schaefer 1974 ). Those that form over the Great Plains of the United States are the most widely studied and are considered as a preferential zone for convection initiation ( Wilson and Roberts 2006 ) which can lead, under favorable conditions, to severe weather events ( Lin 2007 ). Drylines are also found in other

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