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C. W. Newton

DECEMBER 1954C. W. NEWTON449FRONTOGENESIS AND FRONTOLYSIS AS ATHREE-DIMENSIONAL PROCESS By C. W. NewtonWoods Hole Oceanographic Institution 1 and University of Chicago 2.3 (Manuscript received 12 May 1954)ABSTRACTA detailed analysis is presented to show the atmospheric structure during the earlier formative stagesof a deep, upper trough. Over the western United States, a well-marked west-east frontal layer extendsthrough the whole troposphere; in upper levels, this disappears

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George Tai-Jen Chen, Chung-Chieh Wang, and An-Hsiang Wang

over southern China but temperatures there were only 18°–21°C ( Figs. 8f , 1c ), a clear indication for the existence of CAA at low levels. 4. Frontogenetical function and processes Using the method described in section 2b , the 2D frontogenetical function of Ninomiya (1984) was calculated. The interpretation of the pattern of F in relation to the frontal thermal gradient pattern follows the principle below: intensification (weakening) of the front or frontogenesis (frontolysis) occurs when

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David R. Novak, Brian A. Colle, and Ron McTaggart-Cowan

at 700 hPa beneath the upper PV elongation in the cyclone’s dry slot ( Fig. 20b ). Piecewise inversion of these anomalies confirmed that the diabatic PV anomaly in eastern New England was dominant in creating frontolysis (not shown). Frontolysis values induced by the diabatic PV anomaly at 2100 UTC 12 February were ∼25% of the total balanced frontogenesis. Thus, as with the 25 December 2002 case, a diabatic PV anomaly helped shift height falls east of the primary band, and weakened frontogenesis

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David M. Schultz and Joseph M. Sienkiewicz

divergence: where E is the resultant deformation and β is the local angle between an isentrope and the axis of dilatation. Positive regions of frontogenesis indicate where isentropes are instantaneously being brought together by the horizontal flow, thereby increasing the horizontal potential temperature gradient. Negative regions of frontogenesis (or frontolysis) indicate where isentropes are instantaneously being spread apart by the horizontal flow, thereby weakening the horizontal potential

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Shun Ohishi, Tomoki Tozuka, and Meghan F. Cronin

et al. 2008 ; Ogawa et al. 2012 ). Although the importance of SST fronts associated with western boundary currents and their extensions has been recognized, past studies did not investigate reinforcement and relaxation processes for the SST fronts, that is, frontogenesis and frontolysis, in a quantitative manner. Recently, using observational datasets and outputs from a high-resolution coupled general circulation model (CGCM), Tozuka and Cronin (2014) and Ohishi et al. (2016) quantitatively

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Andrea Buzzi

to clarify the physical differences between F 2 and F 3 . The first is significant in the context of upper-level frontogenesis, although it represents only an ideal kinematic process: a pure rotation 1 of the vector ∇ 3 θ in its vertical plane, without change of its magnitude, would not be associated with frontogenesis (or frontolysis) according to F 3 . In contrast, rotation of ∇ 3 θ in the vertical plane associated with strong horizontal gradients of vertical velocity represents the

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Michael J. Reeder, Thomas Spengler, and Clemens Spensberger

gradient (their Figs. 3a,b) is comparable to the pattern of climatological mean diabatic frontogenesis found here ( Fig. 3d ), with frontogenesis along the SST front, strong frontolysis on the southeastern side, and weak frontolysis on the northwestern side. Similar results were found in a general circulation model by Parfitt et al. (2016) . In the present study, however, most of the diabatic frontogenesis along the SST front is associated with no front conditions (cf. Fig. 3d with Fig. 3f

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Carl M. Thomas and David M. Schultz

.e., frontolysis) were also created ( Fig. 12 ). The regions of frequent regions of frontolysis were similar to those for frontogenesis, although there were some minor quantitative differences (cf. Figs. 11 and 12 ). Fig . 12. Frequency of 850-hPa Petterssen frontolysis less than −0.15 K (100 km) −1 (3 h) −1 (%, colored according to scale) for (a) December, (b) March, (c) June, and (d) September. When is used in the frontogenesis function, the similarity between ) and ) is also apparent (cf. Figs

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Lia Siegelman

equation of the evolution of a buoyancy gradient is given by (5) 1 2 d | ∇ b | 2 d t = F s + ∇ w ⋅ ∇ b , with w being the vertical velocity field ( Hoskins 1982 ). A positive F s indicates the presence of frontogenesis, and a negative F s indicates the presence of frontolysis (i.e., frontal destruction). The exact location of the submesoscale fronts is apparent in the buoyancy anomaly field (blue curve in Fig. 13 ), which exhibits a sharp jump down to 299 m in both fronts. The fronts are

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Leif Thomas and Raffaele Ferrari

the vertical vorticity. Equation (6) highlights the various phenomena that can result in restratification (or destratification) of the ocean: frontogenesis or frontolysis (FRONT), advection of PV (ADV), friction (FRIC), and diabatic processes (DIA). If the vertical levels z t and z b do not intersect surface and benthic boundary layers, then advection of PV through the bounding surfaces dominates over the other three terms: diabatic and frictional effects are weak away from boundaries, while

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