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Forest Cannon
,
Jason M. Cordeira
,
Chad W. Hecht
,
Joel R. Norris
,
Allison Michaelis
,
Reuben Demirdjian
, and
F. Martin Ralph

February 2017 case study is also apparent in an evaluation of 192 GPM-DPR transects across ARs during October–April 2014–18. The 192 transects are partitioned into the 65 (one-third of the total) that contained the largest frontogenesis values in the AR transect and compared to the 65 with the weakest frontogenesis values (negative values indicate frontolysis). Note that the centroids of the individual AR transects in the high- and low-frontogenesis populations are scattered spatially so that the

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Callum J. Shakespeare
and
Andrew McC. Hogg

-forced components. A positive value indicates sharpening of frontal gradients (frontogenesis), and a negative value indicates weakening (frontolysis). Fig . 5. Surface layer. Snapshot of (a) the vorticity Rossby number , the mean kinetic energy (m 2 s −2 ) and, (c) the horizontal buoyancy gradient magnitude (s −2 ). (d) Time-averaged mean frontogenesis function [Eq. (8) ; s −3 ]. (e) The depth-integrated and time-averaged MTW conversion (mW m −2 ). (f) The zonal average of (e) in black; average over only

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Xiaolong Yu
,
Alberto C. Naveira Garabato
,
Adrian P. Martin
,
Christian E. Buckingham
,
Liam Brannigan
, and
Zhan Su

OSMOSIS moorings, we document the probability distribution function (PDF) of the outer frontogenesis function in different seasons ( Fig. 9a ). The dominant feature is the marked asymmetry between frontogenesis (i.e., positive ) and frontolysis (i.e., negative ) during winter and spring, when frontogenetic processes are intensified (with exceeding 1 × 10 −20 s −5 , or 0.63) relative to frontolytic processes, albeit for less than 15% of the time. Over 95% of the values of during the fall and

Open access
Matthew Archer
,
Amandine Schaeffer
,
Shane Keating
,
Moninya Roughan
,
Ryan Holmes
, and
Lia Siegelman

denser water ( Spall 1995 ; Manucharyan and Timmermans 2013 ; see section 5b ). However, when a large-scale deformation field is present, instead of the frontal jet devolving into a field of eddies, it remains quasistationary, oscillating between periods of meander growth and decay as the mesoscale frontogenesis counteracts frontolysis by instabilities ( Spall 1997 ). This is a qualitatively similar situation to the frontal jet observed here that is quasistationary and coherent–at times straight

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Mankin Mak
,
Yi Lu
, and
Yi Deng

its long tentacles bunching up together like the isotherms along the cold front. A positive value of F 2 would mean local frontogenesis and negative value local frontolysis. Movement of a front would manifest as closely packed bands of F 2 values in alternating signs. The F 2 values in the plots quantify the local impact of the physical processes at different parts of the two fronts during their development. For example, there are several pairs of short and broad mesoscale green and red

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Kaushik Srinivasan
,
James C. McWilliams
,
Lionel Renault
,
Hristina G. Hristova
,
Jeroen Molemaker
, and
William S. Kessler

mixed layer eddies (MLEs) and fronts ( Fox-Kemper et al. 2008 ; Capet et al. 2008a ) with horizontal scales ~10 km or less. MLEs are stronger for larger horizontal buoyancy gradients ∇ h b and deeper mixed layers H b and are an important reason for the significant enhancement in SM activity during winter. Frontogenesis, originally identified in the context of the atmosphere ( Hoskins and Bretherton 1972 ), occurs when the mesoscale eddy strain field enhances ∇ h b in the mixed layer through the

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Jung Hoon Shin
and
Da-Lin Zhang

surface temperature (SST), and increasing vertical wind shear (VWS) and baroclinicity ( Klein et al. 2000 ; Jones et al. 2003 ). Perhaps the most prominent structural change of an ET TC is the development of an extensive coverage of clouds and precipitation associated with warm frontogenesis when it interacts with low-level baroclinicity to the north ( Harr and Elsberry 2000 ; Klein et al. 2000 ; Atallah and Bosart 2003 ; Colle 2003 ). After its warm core is replaced by a cold core, the TC may

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Takeyoshi Nagai
,
Amit Tandon
,
Eric Kunze
, and
Amala Mahadevan

( Kunze 1985 ; Whitt and Thomas 2013 ) and wind-generated waves may stall in fronts long after forcing. While these alternative possibilities cannot be discounted based on available data, here these observations motivate numerical investigation into the hypothesis that the observed near-inertial shear arises from internal dynamics associated with frontogenesis (frontal strengthening) and frontolysis (frontal weakening) of the Kuroshio Front. 3. Model simulation of the Kuroshio Front a. Model setup We

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Ryusuke Masunaga
,
Hisashi Nakamura
,
Takafumi Miyasaka
,
Kazuaki Nishii
, and
Youichi Tanimoto

frontogenesis processes through a frontogenesis function F (e.g., Miller 1948 ; Hoskins 1982 ; Ogura and Portis 1982 ), which is usually expressed as a time tendency in horizontal gradient of potential temperature in terms of divergence and deformation wind fields. In the present study, however, we slightly modify the frontogenesis function by expressing it as a time tendency of near-surface air temperature gradient. The particular expression may be derived from the thermodynamic equation for MABL on a

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Andrew C. Winters
,
Daniel Keyser
, and
Lance F. Bosart

, https://doi.org/10.1175/1520-0469(1949)006<0330:CTOTHT>2.0.CO;2 . 10.1175/1520-0469(1949)006<0330:CTOTHT>2.0.CO;2 Newton , C. W. , 1954 : Frontogenesis and frontolysis as a three-dimensional process . J. Meteor. , 11 , 449 – 461 , https://doi.org/10.1175/1520-0469(1954)011<0449:FAFAAT>2.0.CO;2 . 10.1175/1520-0469(1954)011<0449:FAFAAT>2.0.CO;2 Nielsen-Gammon , J. W. , and R. J. Lefevre , 1996 : Piecewise tendency diagnosis of dynamical processes governing the development of an upper

Open access