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Chao He, Bo Wu, Liwei Zou, and Tianjun Zhou

1. Introduction The atmospheric circulation over subtropical oceans is dominated by basin-scale anticyclones in summer, associated with subsidence, low-level divergence, and anticyclonic wind curl ( Fig. 1 ). The subtropical anticyclones are responsible for the formation of monsoons, subtropical deserts, and Mediterranean-type climate. Given its profound climatic impact, the formation mechanism for the subtropical anticyclone has been thoroughly studied ( Ting 1994 ; Chen et al. 2001

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Justin E. Jones and Judah Cohen

1. Introduction Strong polar anticyclones are a prominent climatological feature across the high-latitude continental landmasses of the Northern Hemisphere during the cool season and are often associated with intense equatorward cold surges that can in turn have an adverse impact on the human population. These anticyclones are known to develop in response to a number of thermodynamical and dynamical factors. Early research has suggested that thermodynamic arguments (e.g., radiational cooling

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Takafumi Miyasaka and Hisashi Nakamura

1. Introduction Most of the subtropical anticyclones reside over the eastern portions of the subtropical ocean basins throughout the year. In the Northern Hemisphere (NH), they show apparent seasonal variability in their strength and configuration. Each of them strengthens and develops into a basin-wide cell-type configuration in summer. The surface wind stress curl associated with these anticyclones contributes to the maintenance of subtropical oceanic gyres, with warm poleward western

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Thando Ndarana, Mary-Jane Bopape, Darryn Waugh, and Liesl Dyson

(COL) pressure system that was associated with a ridging Atlantic Ocean high pressure system or anticyclone. In this context, the ridging anticyclone is defined as a closed Atlantic Ocean high pressure system that extends eastward to cross the 25°E meridian (further details are shown in Fig. 1 and discussed in section 2 ). The COL extended a low to the surface along the east coast of South Africa. The high pressure system ridged strongly south of the country causing a tight pressure gradient

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Leong Wai Siu and Kenneth P. Bowman

Montgomery streamfunction Ψ at 370 K (black solid contours; interval: 0.5 kJ kg −1 ). The location of the global maximum of Ψ along the zero-wind lines ( u = 0) is indicated by red crosshairs. Climatological positions of the Asian and North American monsoon anticyclones, midoceanic troughs, and westerly ducts are labeled and indicated by arrows. The regional precipitation patterns drive two large-scale anticyclonic circulations ( Fig. 1 ) in the Northern Hemisphere upper troposphere and lower

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Maria Hatzaki, Helena A. Flocas, Ian Simmonds, John Kouroutzoglou, Kevin Keay, and Irina Rudeva

1. Introduction Short-term weather variations in extratropical regions are largely determined by cyclones and anticyclones. Along with cyclones, anticyclonic transports contribute to the maintenance of the general circulation ( Wallace et al. 1988 ; Trenberth 1991 ). There have been many studies of cyclones and these have been prompted by the direct link of these systems to active weather and rapid development. By contrast, climatological studies of anticyclones are few, even though

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Yanjuan Guo, Toshiaki Shinoda, Bin Guan, Duane E. Waliser, and Edmund K. M. Chang

and seasons, and analysis on a global domain and in all seasons is desirable. In addition to the close connection of ARs to extratropical cyclones, recent studies suggest the possible role of anticyclones in generating ARs ( Payne and Magnusdottir 2014 ; Zhang et al. 2019 ). For example, Payne and Magnusdottir (2014) suggested that the development of anticyclonic Rossby wave breaking in the eastern Pacific Ocean plays a significant role in generating landfalling ARs along the west coast of

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Gaële Perret, Thomas Dubos, and Alexandre Stegner

1. Introduction In situ measurements and general circulation models have shown that large-scale vortices, that is, eddies whose characteristic length scale is larger than the local deformation radius, are ubiquitous in the oceans ( Olson 1991 ; McWilliams 1985 ). A striking characteristic of these large-scale and long-lived structures is that anticyclonic vortices tend to be more prevalent than cyclonic ones. Large-scale anticyclones are frequently observed in the lee of an oceanic archipelago

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Sumant Nigam and Steven C. Chan

1. Introduction Subtropical sea level pressure anticyclones—majestic semipermanent features over the northern and southern oceans—are an integral element of the atmospheric general circulation: their clockwise (in the Northern Hemisphere) near-surface flow connects the tropical trade wind regime with the midlatitude westerly belt, influencing both. Thermodynamically, the anticyclones reside between the intense convection zones in the deep tropics and the midlatitude storm tracks that extend

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Aviv Solodoch, Andrew L. Stewart, and James C. McWilliams

1. Introduction In several ocean basins, long-lived and semistationary mesoscale anticyclones (ACs) appear above topographic bowls. 1 Examples are the Mann Eddy ( Mann 1967 ), Lofoten Basin Eddy (e.g., Ivanov and Korablev 1995 ; Köhl 2007 ; Søiland et al. 2016 ), and the Rockall Trough Eddy ( Le Corre et al. 2019 ). The eddies have a clear climatological signature in sea surface height, as seen from satellite altimetry ( Fig. 1 ). The first two have been repeatedly sampled in hydrographic

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