scholarly journals Baroclinic Flow around Planetary Islands in a Double Gyre: A Mechanism for Cross-Gyre Flow

2010 ◽  
Vol 40 (5) ◽  
pp. 1075-1086
Author(s):  
Joseph Pedlosky
Keyword(s):  
Vertical Structure ◽  
Vertical Mixing ◽  
Ocean Bottom ◽  
Layer Model ◽  
Buoyancy Forcing ◽  
Pressure Anomaly ◽  
Two Layer Model ◽  
Baroclinic Flow ◽  
Double Gyre

Abstract A quasigeostrophic, two-layer model is used to study the baroclinic circulation around a thin, meridionally elongated island. The flow is driven by either buoyancy forcing or wind stress, each of whose structure would produce an antisymmetric double-gyre flow. The ocean bottom is flat. When the island partially straddles the intergyre boundary, fluid from one gyre is forced to flow into the other. The amount of the intergyre flow depends on the island constant, that is, the value of the geostrophic streamfunction on the island in each layer. That constant is calculated in a manner similar to earlier studies and is determined by the average, along the meridional length of the island, of the interior Sverdrup solution just to the east of the island. Explicit solutions are given for both buoyancy and wind-driven flows. The presence of an island of nonzero width requires the determination of the baroclinic streamfunction on the basin’s eastern boundary. The value of the boundary term is proportional to the island’s area. This adds a generally small additional baroclinic intergyre flow. In all cases, the intergyre flow produced by the island is not related to topographic steering of the flow but rather the pressure anomaly on the island as manifested by the barotropic and baroclinic island constants. The vertical structure of the flow around the island is a function of the parameterization of the vertical mixing in the problem and, in particular, the degree to which long baroclinic Rossby waves can traverse the basin before becoming thermally damped.

On the Thickness Ratio in the Quasigeostrophic Two-Layer Model of Baroclinic Instability

2013 ◽  
Vol 70 (5) ◽  
pp. 1505-1511 ◽  
Author(s):  
Noboru Nakamura ◽  
Lei Wang
Keyword(s):  
Growth Rate ◽  
Vertical Structure ◽  
Lower Layer ◽  
Baroclinic Instability ◽  
Thickness Ratio ◽  
Layer Model ◽  
Optimal Thickness ◽  
Zonal Wavenumber ◽  
The Mean ◽  
Two Layer Model

Abstract It is shown that the classical quasigeostrophic two-layer model of baroclinic instability possesses an optimal ratio of layer thicknesses that maximizes the growth rate, given the basic-state shear (thermal wind), beta, and the mean Rossby radius. This ratio is interpreted as the vertical structure of the most unstable mode. For positive shear and beta, the optimal thickness of the lower layer approaches the midheight of the model in the limit of strong criticality (shear/beta) but it is proportional to criticality in the opposite limit. For a set of parameters typical of the earth’s midlatitudes, the growth rate maximizes at a lower-layer thickness substantially less than the midheight and at a correspondingly larger zonal wavenumber. It is demonstrated that a turbulent baroclinic jet whose statistical steady state is marginally critical when run with equal layer thicknesses can remain highly supercritical when run with a nearly optimal thickness ratio.

Coherent structures of nonlinear barotropic-baroclinic interaction in unequal depth two-layer model

2021 ◽  
Vol 408 ◽  
pp. 126347
Author(s):  
Jiaqi Zhang ◽  
Ruigang Zhang ◽  
Liangui Yang ◽  
Quansheng Liu ◽  
Liguo Chen
Keyword(s):  
Coherent Structures ◽  
Layer Model ◽  
Two Layer Model

Propagation and localization of Rossby waves over random topography (two-layer model)

Wave Motion ◽  
1998 ◽  
Vol 28 (4) ◽  
pp. 333-352 ◽  
Author(s):  
V.I. Klyatskin ◽  
N.V. Gryanik ◽  
D. Gurarie
Keyword(s):  
Rossby Waves ◽  
Layer Model ◽  
Two Layer Model

Permafrost mapping by audiofrequency magnetotellurics

1978 ◽  
Vol 15 (10) ◽  
pp. 1539-1546 ◽  
Author(s):  
A. Koziar ◽  
D. W. Strangway
Keyword(s):  
Mackenzie Delta ◽  
Conductive Layer ◽  
Frequency Range ◽  
Layer Model ◽  
Resistive Layer ◽  
Asymptotic Models ◽  
Two Layer Model ◽  
Electrical Methods ◽  
Permafrost Mapping ◽  
Lateral Variations

The audiofrequency magnetotelluric (AMT) method has been used to study permafrost thickness near Tuktoyaktuk, N.W.T. in the Mackenzie Delta. In the frequency range of 10 Hz–10 kHz the permafrost behaves as a simple resistive layer over a conductive layer. This simple two-layer model can be inverted by asymptotic models to give a unique value for the thickness of the highly resistive frozen layer. In areas of simple layering, these results correlate well with drilling. In areas of sharp lateral variations in resistivity, depths tend to be underestimated. Unlike other electrical methods, AMT is not hampered by the presence of a surface melt layer in the summer if the conductivity–thickness product of this 'active layer' is less than about 0.03 mho (0.03 S).

The Nature of Boxy/Peanut Spiral Galaxies: Overview and New Results

1997 ◽  
Vol 14 (2) ◽  
pp. 146-158 ◽  
Author(s):  
M. Bureau ◽  
K. C. Freeman
Keyword(s):  
Formation Mechanism ◽  
Vertical Structure ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Spiral Galaxies ◽  
Physical Conditions ◽  
Bar Buckling ◽  
Line Imaging ◽  
Observational Program

AbstractThe formation mechanism of boxy/peanut-shaped bulges in spiral galaxies has been a problem for many years. We briefly review here the possible formation scenarios for boxy/peanut bulges, concentrating on both the bar-buckling and accretion hypotheses, and then describe an observational program aimed at testing those various theories and studying the vertical structure of edge-on bars. Our program includes optical long-slit spectroscopy, Hiline-imaging, near-infrared imaging, and multi-band optical imaging. New spectroscopic results (both optical and Hi) are presented on seven galaxies, including five boxy/peanut-bulge spirals. Based on Kuijken & Merrifield's (1995) idea for detecting edge-on bars, we argue that these observations constitute a strong case in favour of the bar-buckling mechanism for the formation of boxy/peanut-shaped bulges, but they also raise many questions and prompt for more detailed modelling to be made. The implications of the observations concerning the determination of rotation curves and of the physical conditions in bulges are also discussed.

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