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

, Santos et al. (2009) analyzed the occurrence of strong and persistent ridge events (SPREs) over the southeastern North Atlantic and described the associated large-scale meteorological conditions. SPREs are commonly characterized by a strengthening of the North Atlantic ridge, a northward shift of the North Atlantic storm track, and an enhanced diffluence of the subtropical and eddy-driven westerly jets over the North Atlantic. During SPREs there is also clear evidence for a warm-core equivalent

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Gwendal Rivière

1. Introduction Because of increased amounts of greenhouse gases (GHGs), several changes in the atmospheric general circulation have been noted in future climate Intergovernmental Panel on Climate Change (IPCC) scenarios relative to the present climate. Among them, there is a rise in the height of the tropopause ( Lorenz and DeWeaver 2007 ), an increase in the dry static stability ( Yin 2005 ; Frierson 2006 ), and a poleward shift of the tropospheric jet streams and storm tracks. This is seen

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Osamu Isoguchi and Hiroshi Kawamura

been resolved by satellite observations over the last decade. Satellite scatterometers provide us maps of the surface vector wind with spatial resolution of 25 km ( Liu 2002 ), and they are operationally assimilated into weather prediction models. They have succeeded in showing orographically modified wind fields, such as surface wind jets and wakes, and have allowed us to examine detailed features, formation mechanisms, and oceanic responses to them (e.g., Laing and Brenstrum 1996 ; Kawamura and

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Shuguang Wang, Fuqing Zhang, and Chris Snyder

1. Introduction Gravity waves propagating vertically from the lower atmosphere are widely recognized to play important roles in a variety of atmospheric phenomena. Known sources of these gravity waves include mountains, moist convection, fronts, upper-level jets, geostrophic adjustment, and spontaneous generation ( Fritts and Alexander 2003 , and references therein). Among these, jets are often responsible for generating low-frequency inertia–gravity waves with characteristic horizontal

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Joseph Bernstein and Brian Farrell

describing both the turbulence and the eddy–mean flow interaction. The simplest idea available is eddy diffusivity of potential vorticity (PV). The main drawback of this method is that it fails to capture the upgradient momentum fluxes commonly observed in the midlatitude jet. Jin et al. (2006) propose a model describing the eddy–mean flow interactions that has success reproducing observed patterns. However, the climatological eddy variance in the model is fit to observations. The model we choose is

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D. Alex Burrows, Craig R. Ferguson, and Lance F. Bosart

1. Introduction U.S. Great Plains (GP) low-level jets (GPLLJs) are a predominant source of warm-season climate variability at diurnal to subseasonal time scales. GPLLJ frequencies range from 70% to 97%, 33% to 72%, and 58% to 75% of May–September (MJJAS) nights in the southern Great Plains (SGP), central Great Plains (CGP), and northern Great Plains (NGP), respectively ( Burrows et al. 2019a ). GPLLJs contribute to nocturnal wind and rainfall maxima (e.g., Helfand and Schubert 1995 ; Higgins

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Rei Chemke and Yohai Kaspi

Rhines scale because of the opposite dependence of frequency on wavenumber in the turbulent and Rossby waves regimes ( Rhines 1975 ; Holloway and Hendershott 1977 ; Rhines 1979 ; Danilov and Gurarie 2000 ; Galperin et al. 2006 ; Kaspi and Flierl 2007 ). Nonetheless, the inverse energy cascade continues up to the zero zonal wavenumber, and formation of zonal jets occurs (e.g., Rhines 1977 ; Williams 1978 ; Rhines 1994 ), with a meridional wavenumber following the Rhines scale ( Rhines 1975

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B. J. H. Van de Wiel, A. F. Moene, G. J. Steeneveld, P. Baas, F. C. Bosveld, and A. A. M. Holtslag

1. Introduction More than 50 years ago, Blackadar (1957 ; hereafter B57) introduced his conceptual model for nocturnal inertial oscillations. Since then, it has been generally known that inertial oscillations (IOs) form an important mechanism behind the occurrence of low-level wind maxima or low-level jets (LLJs)—for example, in Australia and over the European plains ( Thorpe and Guymer 1977 ; Van Ulden and Wieringa 1996 ; Baas et al. 2009 ). Low-level jets are not solely initiated by IOs

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Riwal Plougonven and Chris Snyder

Dunkerton 1995 ; Zhang 2004 ) have emphasized at least two classes of waves being generated. These studies agree with evidence from observations [e.g., the key role of jet exit regions ( Uccellini and Koch 1987 )], but do not investigate other aspects, such as waves associated with upper-level troughs ( Plougonven et al. 2003 ) or surface fronts ( Eckermann and Vincent 1993 ). The latter have also been identified in numerical simulation of two-dimensional frontogenesis ( Snyder et al. 1993 ). In this

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Ara Arakelian and Francis Codron

1. Introduction The atmospheric variability over the Southern Ocean is dominated at time scales longer than a week by zonally symmetric meridional fluctuations of the jet, a structure known as the southern annular mode (SAM). The SAM also has a large impact on the ocean ( Sen Gupta and England 2006 ) and often dominates the regional response to external forcings, such as greenhouse gas increase, ozone depletion ( Gillett and Thompson 2003 ; Perlwitz et al. 2008 ; Son et al. 2010 ), or El Niño

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