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Alexander Lemburg, Jürgen Bader, and Martin Claussen

1. Introduction Rainfall in sub-Saharan West Africa is inextricably linked to the West African monsoon (WAM), which is characterized by a pronounced seasonal wind shift initiated by thermodynamic contrasts between land and ocean. A prominent feature of the summertime WAM circulation is the tropical easterly jet (TEJ), an upper-tropospheric (100–200 hPa) easterly current between 5° and 20°N, first described by Rao (1952) and Koteswaram (1958) . The TEJ originates in the South Asian monsoon

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Melissa A. Nigro, John J. Cassano, Matthew A. Lazzara, and Linda M. Keller

Hemisphere) as a left-side jet. Seefeldt and Cassano (2008) referred to the area of maximum wind speed off the coast of the Prince Olav Mountains as the Queen Maud Mountains tip jet. Tip jets have been studied off the coast of Greenland. The Greenland easterly tip jet ( Moore and Renfrew 2005 ; Renfrew et al. 2009 ; Outten et al. 2009 ) is driven by the same forcing mechanisms as the Northern Hemisphere left-side jet ( Barstad and Gronas 2005 ). The Greenland easterly tip jet occurs when a low

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Maurício I. Oliveira, Ernani L. Nascimento, and Carolina Kannenberg

1. Introduction A low-level jet (LLJ) is an airstream whose vertical profile displays a wind speed maximum in the lower troposphere. More than one atmospheric mechanism is known to generate LLJs (e.g., Stensrud 1996 ; Shapiro et al. 2016 ), with the implication that an LLJ can manifest itself in different ways. A first general class of LLJ results from the diurnal cycle of coupling and decoupling of the surface layer from the boundary layer above leading to an inertial oscillation that

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Qingfang Jiang, Shouping Wang, and Larry O’Neill

1. Introduction Satellite observations and numerical modeling studies have shown that a low-level equatorward jet frequently occurs offshore of the central Chilean coast [i.e., the Chilean low-level coastal jet (CLLCJ)] under the influence of the semipermanent Southeast Pacific high pressure (SEPH) system ( Fig. 1 ). The definitions, characteristics, and formation mechanisms of a variety of low-level jets have been reviewed by Stensrud (1996) . In this study, we define a coastal low-level jet

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João A. Santos, Tim Woollings, and Joaquim G. Pinto

clarify the mechanisms underlying the atmospheric variability over the NA under current climate conditions. Among the possible diagnostics for this variability, the eddy-driven westerly jet is an important indicator of the physical state of the tropospheric circulation within the Euro-Atlantic sector. In particular, its latitude and speed have been shown to be suitable measures of the largest-scale circulation over this region ( Woollings et al. 2010b ). When considering the jet latitude, the two

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Murong Zhang and Zhiyong Meng

distribution (red dots) in Guangdong Province. The low-level jet (LLJ) is commonly observed in southern China during presummer rainy season (e.g., Du et al. 2014 ; Luo et al. 2017 ). The LLJs over this region can be generally classified into two types ( Chen et al. 1994 ; Du et al. 2012 , 2014 ).The first type is synoptic-system-related LLJ (SLLJ), which occurs within low-level free troposphere (900–600 hPa); the second type is boundary layer jet (BLJ), which occurs in the boundary layer and can be

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Elizabeth N. Smith, Joshua G. Gebauer, Petra M. Klein, Evgeni Fedorovich, and Jeremy A. Gibbs

1. Introduction Wind maxima called nocturnal low-level jets (NLLJs) often occur during the night in the lowest kilometer of the atmosphere. In the most general sense, the NLLJ is the result of the disruption of the daytime force balance between the Coriolis, pressure gradient, and frictional forces. Once the sun sets, thermally generated turbulence decays, and the stable boundary layer (SBL) forms. The frictional force weakens above the surface, which eliminates the force balance and leads to

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Joseph A. Grim, Robert M. Rauber, Greg M. McFarquhar, Brian F. Jewett, and David P. Jorgensen

1. Introduction Mesoscale convective systems (MCSs) are common during the late spring and summer across the central United States ( Johns 1993 ) and are frequently associated with strong straight-line winds. Common features of many mature MCSs include the leading convective line, front to rear flow aloft, and a rear inflow jet (RIJ; e.g., Houze 2004 ). MCS squall lines sometimes form bow-shaped lines of convective cells, termed bow echoes ( Fujita 1978 ), that can be associated with damaging

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Stanley B. Trier and Robert D. Sharman

1. Introduction Cruising altitudes for commercial aviation located near tropopause jet streams are predisposed to turbulence hazards (e.g., Shapiro 1978 ; Kennedy and Shapiro 1980 ; Sharman et al. 2012 ). Strong vertical shear of the horizontal wind near such jet streams can lead to Kelvin–Helmholtz instability (KHI), which is often invoked (e.g., Reiter 1969 ; Dutton and Panofsky 1970 ; Browning and Watkins 1970 ) as a mechanism to explain clear-air turbulence (CAT). Inertia

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Matthew A. Campbell, Craig R. Ferguson, D. Alex Burrows, Mark Beauharnois, Geng Xia, and Lance F. Bosart

1. Introduction The U.S. Great Plains (GP) is currently well studied in the hydrological and meteorological communities for two main reasons: 1) it serves as the corridor of a prominent low-level jet (LLJ) and 2) it is a “hot spot” for modeled land–atmospheric coupling strength. Both research themes are socially motivated by the need to better understand and predict precipitation in a region that is highly susceptible to seasonal droughts, such as the 2012 “flash drought” (e.g., Hoerling et al

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