Physical influences on east coast cyclogenesis

Danard, Maurice B.; Ellenton, G.

doi:10.1080/07055900.1980.9649078

Cited by 32 publications

(15 citation statements)

References 24 publications

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“…D1 represents the Ekman pumping and B1 the w-source due to horizontal differential heating/salting. The same expression can be found in atmospheric studies (Danard and Ellenton 1980;Giordani 1997). Terms D2, B2 are activated only when a surface energy input (τ y0 ; F 0 ; @F 0 @x ) and an MLD horizontal variability @h @x ; @ 2 h @x 2 occur simultaneously.…”

Section: Analytical Approachsupporting

confidence: 58%

Advanced insights into sources of vertical velocity in the ocean

2006

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Estimating vertical velocity in the oceanic upper layers is a key issue for understanding ocean dynamics and the transport of biogeochemical elements. This paper aims to identify the physical sources of vertical velocity associated with sub-mesoscale dynamics (fronts, eddies) and mixed-layer depth (MLD) structures, using (a) an ocean adaptation of the generalized Q-vector form of the ω-equation deduced from a primitive equation system which takes into account the turbulent buoyancy and momentum fluxes and (b) an application of this diagnostic method for an ocean simulation of the Programme Océan Multidisciplinaire Méso Echelle (POMME) field experiment in the North-Eastern Atlantic. The approach indicates that wsources can play a significant role in the ocean dynamics and strongly depend on the dynamical structure (anticyclonic eddy, front, MLD, etc.). Our results stress the important contribution of the ageostrophic forcing, even under quasigeostrophic conditions. The turbulent w-forcing was split into two components associated with the spatial variability of (a) the buoyancy and momentum (Ekman pumping) surface fluxes and (b) the MLD. Process (b) represents the trapping of the buoyancy and momentum surface energy into the MLD structure and is identified as an atmosphere/ oceanic mixed-layer coupling. The momentum-trapping process is 10 to 100 times stronger than the Ekman pumping and is at least 1,000 times stronger than the buoyancy w-sources. When this decomposition is applied to a filamentary mixed-layer structure simulated during the POMME experiment, we find that the associated vertical velocity is created by trapping the surface wind-stress energy into this structure and not by Ekman pumping.

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Section: Analytical Approachsupporting

confidence: 58%

Advanced insights into sources of vertical velocity in the ocean

2006

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“…Sanders and Gyakum (1980) found that cyclogenesis occurred in a relatively smooth area of the sea state from observational data. Danard and Ellenton (1980) numerically showed that the contrast in frictional drag was responsible for cyclone deepening over water while under similar conditions no deepening would take place over land.…”

Section: Introductionmentioning

confidence: 99%

Favorable environments for explosive cyclogenesis in a modified two-layer Eady model

Weng

Barcilon

1987

Tellus A: Dynamic Meteorology and Oceanography

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A modified two-layer Eady model is used to find favorable environments for explosive cyclogenesis by examining baroclinic instability of both short and long waves. The model includes Ekman dissipation and low-level sensible heating, and allows both static stabilities and vertical shears to be different bui constant in each layer. It is found that an enhanced lowlevel shear, a reduced low-level static stability, a relatively large upper-level static stability, and an appropriate height of the interface are favorable for the short-wave development, and that an enhanced upper-level shear and a relatively small upper-level static stability are favorable for the long-wave development, while having opposite effects on the short wave. A small Ekman dissipation is favorable for the development of both waves. Newtonian sensible heating does not directly enhance the development of both waves. A favorable environment for explosive cyclogenesis may not be expressed by a single parameter, but rather by a combination of baroclinic instability with several parameters which contribute collectively to the development of both short and long waves. The relative phase of these waves also plays an important part: the development is enhanced when the surface cyclone is ahead of the upper level wave trough by in.

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“…Although undoubtedly most synoptic scale disturbances in midlatitude regions are baroclinic in origin, possible cumulus effects have been suggested. Results obtained in many studies, however, have been less than conclusive (e.g., Danard and Ellenton, 1980;Rasmussen, 1979). The extent of the influence of cumulus clouds in extratropical systems is not yet well understood.…”

Section: Introductionmentioning

confidence: 99%

“…and the maritime provinces of Canada are often observed during the late winter seasons. The amounts of precipitation observed in these storms are often as high as 35-40 mm/day (Danard and Ellenton, 1980), although it is not clear how much of it is produced by cumulus convection, and how much by stratiform clouds.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of quasi-geostrophic systems with cumulus convection

Yip¹,

CHO²

1982

Tellus

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The dynamic effects of a cumulus ensemble on a quasi-geostrophic weather system in the midlatitude region are examined, in addition to the heating due to release of latent heat. It has been found that the effects of the eddy vertical advection of momentum, and the eddy dynamic pressure due to the eddy kinetic energy associated with cumulus clouds are rather small. The only important dynamic effect comes from the ability of clouds to produce a horizontal eddy flux of vertical vorticity. In the momentum equation, this effect appears in the form of an eddy Coriolis force, which may be obtained from the horizontal eddy vorticity flux by rotating it by 90" clockwise. In the vorticity equation, it appears in the form of generation of positive vorticity by convective elements in the lower levels, and generation of negative vorticity in the upper levels.Using Ekman-layer pumping theory as the closure condition, the effects of cumulus convection on baroclinic instability are investigated. It has been found that the growth rate of a baroclinically unstable wave is increased appreciably by the cloud scale processes.Tellus 34 (1982), 1 0040-2826/82/010063-11%02.50/0 0 1982 Munksgaard, Copenhagen

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Physical influences on east coast cyclogenesis

Cited by 32 publications

References 24 publications

Advanced insights into sources of vertical velocity in the ocean

Advanced insights into sources of vertical velocity in the ocean

Favorable environments for explosive cyclogenesis in a modified two-layer Eady model

Dynamics of quasi-geostrophic systems with cumulus convection

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