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Jason C. Shafer
and
W. James Steenburgh

( Fig. 23c ). Further, diabatic frontolysis is occurring along the incipient cold front (not shown for clarity). This F D distribution explains why the total frontogenesis maximum is shifted into the prefrontal environment and occurs because the NARR-analyzed diabatic heating minimum is located along or just ahead of the developing front ( Fig. 23d ). As discussed below, this represents an unrealistic diabatic heating distribution. At −6 h, which represents a composite mean time of 1500 MST, total

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Tao Wang
,
Roy Barkan
,
James C. McWilliams
, and
M. Jeroen Molemaker

tendency is positive in most parts of F1 ( Fig. 5c ), indicating an increase in horizontal velocity gradient at the moment. As shown in Figs. 5d–f , the horizontal advective tendency dominates in frontogenesis, and the vertical mixing term dominates in frontolysis. The vertical advection term is frontolytic, but its absolute value is much smaller than vertical mixing term ( Fig. 5e ). Fig . 5. Instantaneous horizontal patterns of (a) density (colors) and horizontal velocities (arrows), (b) frontal

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Naoko Kitabatake

resolved into natural coordinates ( s , n ) defined by the local orientation of θ e contours in the isobaric surface, such that where Thus the components of the vector frontogenesis in Eq. (3) are given as follows: Negative (positive) F n corresponds to the traditional frontogenesis (frontolysis) defined by Petterssen (1956) , while positive (negative) F s corresponds to the cyclonic (anticyclonic) rotational frontogenesis( Keyser et al. 1988 ; Martin 1999 ; Harr and Elsberry 2000 ). Note

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David M. Schultz
and
John A. Knox

), sea level pressure (black lines every 2 hPa), and 900-hPa frontogenesis [K (100 km) −1 (3 h) −1 , shaded according to scale, solid (dashed) lines surrounding shading represent frontogenesis (frontolysis) values of ±1.5 K (100 km) −1 (3 h) −1 ]. Rectangles identify regions where banded clouds and precipitation were observed from satellite and radar imagery. Fig . 5. Unfiltered, 0.5° elevation-angle, radar reflectivity factor (dB Z ) from the nationwide Weather Surveillance Radar-1988 Doppler

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Sally J. Warner
,
Ryan M. Holmes
,
Elizabeth H. M. Hawkins
,
Martín S. Hoecker-Martínez
,
Anna C. Savage
, and
James N. Moum

both frontogenesis (frontal intensification) and frontolysis (frontal weakening). Frontogenesis occurs when the strain in the velocity field compresses the horizontal distance between lines of constant buoyancy b , and frontolysis occurs when this distance expands. Frontogenesis can be quantified by considering the change in magnitude of the horizontal buoyancy gradient |∇ h b | 2 caused by the advection of buoyancy by horizontal u h = ( u , υ ) and vertical w velocities. The evolution of

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Victoria A. Sinclair
,
Sami Niemelä
, and
Matti Leskinen

, there was little shear and strong stratification, which together lead to a shallower, less turbulent boundary layer than onshore. Horizontal gradients in surface sensible heat fluxes can result in either frontolysis or frontogenesis. Observations of atmospheric variables and measurements of sensible heat fluxes from two SMEARs ( Fig. 14 ), one located at Hyytiälä in central Finland (SMEAR II) and the second at Kumpula in Helsinki (SMEAR III), are analyzed and compared to the AROME forecast. The

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Leah Johnson
,
Craig M. Lee
,
Eric A. D’Asaro
,
Leif Thomas
, and
Andrey Shcherbina

frontogenesis that sharpens lateral buoyancy gradients near the surface. This results in a shallower velocity spectral slope of k −2 , as previously theorized ( Blumen 1978 ; Klein et al. 2008 ; Kunze 2019 ) and observed ( Shcherbina et al. 2013 ; Callies and Ferrari 2013 ). As such, lower estimates of ζ , δ , and α at larger spatial scales are not simply a result of the smoothed submesoscale field but are ultimately associated with different dynamics. For example, strain estimated from AVISO were

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Olivier Marchal

vertical profile of averaged u at a location along the slope ( km). The diffluence of the cross-slope flow near the shelf edge is favorable to frontolysis, as shown by considerations on the frontogenetic function, where is the material derivative ( Hoskins 1982 ). A positive (negative) value of F corresponds to frontogenesis (frontolysis). The function F can also be written as where is a unit vector parallel to the temperature gradient. Let us decompose the temperature T , the vector , and

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Michael A. Spall
,
Robert S. Pickart
,
Peigen Lin
,
Wilken-Jon von Appen
,
Dana Mastropole
,
H. Valdimarsson
,
Thomas W. N. Haine
, and
Mattia Almansi

frontogenesis and instability. In doing so, we demonstrate that the three types of DSOW variability—boluses, pulses, and flooding events—are tied together within a single dynamical framework. Our results thus provide insight regarding the time-dependent flux of overflow water into the Irminger Sea. 2. Data and numerical model a. In situ data The primary in situ data used in the study are from mooring DS1 deployed in Denmark Strait at the deepest part of the sill ( Fig. 1 ). The mooring contains an RDI 75

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Shawn M. Milrad
,
John R. Gyakum
,
Kelly Lombardo
, and
Eyad H. Atallah

back to the Q vector and thus QG vertical motion using where Q is the Q vector, p is the pressure, p o is some reference pressure, R is the gas constant for dry air, and κ is R divided by c p , the specific heat at constant pressure. Frontogenesis and frontolysis are indicated when Q points to warmer and colder air, respectively (e.g., Sanders and Hoskins 1990 ). Figure 4 shows that CSB1 occurs in the left-exit region of a straight northwest–southeast-upper-tropospheric jet

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