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James C. McWilliams, Jonathan Gula, and M. Jeroen Molemaker

1986 ). These polar frontal widths are also much smaller than the length scales of the more general variability associated with the oceanic mesoscale (≈10 2 km) and atmospheric synoptic scale (≈10 3 km) flows engendered by the jet instabilities. Why? The thesis in this paper is that the sharpness of the polar wall is a result of frontogenesis caused by the ageostrophic secondary circulation (i.e., flow in the plane perpendicular to the main geostrophic jet axis) that arises from a combination of

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Bàrbara Barceló-Llull, Enric Pallàs-Sanz, Pablo Sangrà, Antonio Martínez-Marrero, Sheila N. Estrada-Allis, and Javier Arístegui

particular type of anticyclones is intrathermocline eddies, which are subsurface intensified eddies also rotating anticyclonically but with dome-shaped (bowl shaped) isopycnals in the upper (lower) layers ( McGillicuddy et al. 2007 ). Ageostrophic secondary circulation (ASC), which includes the ageostrophic horizontal velocity and the vertical velocity, has an important role within mesoscale structures through the restoring of thermal wind balance. The vertical velocities associated with ASC play an

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Yutaka Yoshikawa, Craig M. Lee, and Leif N. Thomas

1. Introduction The transfer of mixed layer water into the pycnocline, referred to as subduction, sets the flux of heat and tracers from the surface mixed layer into the stratified ocean interior. Previous numerical studies ( Samelson and Chapman 1995 ; Spall 1995 ; Wang 1993 ) find that frontogenesis at a meandering density front can induce a three-dimensional (3D) ageostrophic cross-front circulation that subducts surface water into or below the pycnocline, which can result in the formation

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Arthur Y. Hou and Malcolm K. W. Ko

1396 JOURNAL OF THE ATMOSPHERIC SCIENCES VOL. 46, NO. 10Ageostrophic Effects on the Stratospheric Residual Circulation and Tracer Distributions ARTHUR Y. HOU AND MALCOLM K. W. KoAtmospheric and Environmental Research Inc., Cambridge, Massachusetts(Manuscript meeived 18 April 1988, in final form 19 December 1988) ABSTRACT We have examined all idealize~ zonally averaged, nonlinear

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Chungu Lu, Paul E. Ciesielski, and Wayne H. Schubert

the longevity of certain types of mesoscale convective systems ( Raymond and Jiang 1990 ). An important aspect of these studies is that they allow us to view mesoscale convective systems within the unified theoretical framework of PV dynamics ( Hoskins et al. 1985 ; Haynes and McIntyre 1987 ). A shortcoming of these studies is their lack of emphasis on the ageostrophic part of the squall line circulation. On the other hand, mesoscale meteorologists and cloud physicists are more likely to focus on

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Michael Diaz and Anantha Aiyyer

processes leading to energy dispersion and the genesis of AEW A can be understood with more transparency using the concept of an ageostrophic secondary circulation. Although one can achieve an analogous explanation using PV-advection arguments (e.g., Hoskins et al. 1985 ), the secondary circulation concept relates more directly to the terms in the local EKE budget. To reveal the lower branch of this secondary circulation, we plot divergence, geopotential, and ageostrophic flow at 900 hPa ( Figs. 9a

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Daniel Keyser and Toby N. Carlson

DECEMBER 1984DANIEL KEYSER AN'D TOBY N. CARLSON2465Transverse Ageostrophic Circulations Associated with Elevated Mixed LayersDANIEL KEYSERGoddard Laboratory for Atmospheric Sciences, NASA/Goddard Space Flight Center, Greenbelt, MD 20771TOBY N. CARLSONDepartment of Meteorology, The Pennsylvania State University, University Park, PA 16802(Manuscript received 24 December 1983, in final form 7 August 1984)ABSTRACTAn elevated mixed layer is a principal component of the conceptual model recently

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Daniel Keyser and Michael J. Pecnick

15 JUNE 1985 DANIEL .KEYSER AND MICHAEL J. PECNICK 1283Diagnosis of Ageostrophic Circulations in a Two-Dimensional Primitive Equation Model of Frontogenesis DANIEL KEYSERLaboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 MICHAEL J. PECNICK*General Software Corporation, Landover, MD 20785(Manuscript received 31 May 1984, in final form 5 February

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Zhongya Cai and Jianping Gan

internal responses of the CAC circulation, examined the importance of the interaction between the geostrophic motion and ageostrophic processes, and illustrated the dynamics of the CAC circulation from the perspective of the kinetic energy pathway. This paper is organized as follows: section 2 introduces the numerical model and the kinetic energy analysis methods, section 3 shows the three-dimensional structure of the MKE and EKE in CAC circulation, and section 4 presents our detailed

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S. N. Estrada-Allis, B. Barceló-Llull, E. Pallàs-Sanz, A. Rodríguez-Santana, J. M. A. C. Souza, E. Mason, J. C. McWilliams, and P. Sangrà

(1981) suggested that diabatic mixing can drive ageostrophic secondary circulation at fronts. Nagai et al. (2006) solved the quasigeostrophic (QG) and semigeostrophic (SG) diabatic equations (omega equation), showing that vertical mixing enhances vertical velocity in the upper ocean layers. Pallàs-Sanz et al. (2010) used a K -profile parameterization ( Large et al. 1994 ) of vertical mixing in a generalized omega equation for a California Current System front, and showed that the effects of

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