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1.
L.-Y. Oey 《Continental Shelf Research》1997,17(15):1929-1944
Observations indicate that, perhaps as a result of intense shears produced by the topographic steering of the slope current and merging of the warm North Atlantic water with cold Nordic waters, the Faroe-Shetland Channel is a fertile ground for energetic eddies and meanders. How these meso-scale ( 10 km) features are resolved in a three-dimensional numerical model is studied here with grid-nesting, in which the convergence of the simulated energetics is examined as a function of grid sizes Δ =10, 10/3, 10/5 and 10/7 km. Large-scale forcing to the fine-grid nest consists of steady slope-current transport (2 Sv) and north/south climatological density difference only. The mean fields were found to converge at Δ = 10/3 km, but the eddy fields required Δ = 2 km or less. At the finest grids, meso-scale features more in conformity with those observed were found: meanders with amplitudes of O(10 km) and along-slope propagation speeds of about 0.14 m s- 1 cross-channel vacillation of the slope current, with amplitude of about 10 km and periods of 5–10 days, and vertical excursions of isotherms of O(100 m). The meanders were highly ageostrophic (ζ/f> 1, ζ=relative vorticity, f = Coriolis parameter), and developed as a result of conditions favorable to flow instability originated from south of the channel. When adequately resolved, the meander energetics are comparable to those produced by (large-scale) winds, which suggests that a high-resolution grid (Δ < 2 km) will be required for hindcast and forecast studies. 相似文献
2.
M.S. Oey 《Astrophysics and Space Science》2002,281(1-2):483-486
Two fundamental constraints on the earliest star formation conditions in the Galaxy are an apparent empirical low-metallicity threshold of-4 ? [Fe/H], an and upper limit to the fraction of Population III halo stars of F III < 4 × 10-4. How do these observed constraints compare with predictions of simple models? This is investigated within the framework of element dispersal from clustered core-collapse SNe. Simple arguments considering turbulent mixing within multi-phase ISM suggest that the observed low-metallicity threshold is consistent with rough expected values. However, the observed limit on F III is two orders of magnitude larger than predictions from this simple, one-zone inhomogeneous chemical evolution. 相似文献
3.
Observations indicate that off the northeastern coast of Taiwan a branch of the Kuroshio intrudes farther northward in winter
onto the shelf of the East China Sea. We demonstrate that this seasonal shift can be explained solely by winter cooling. Cooling
produces downslope flux of dense shelf water that is compensated by shelfward intrusion. Parabathic isopycnals steepen eastward
in winter and couple with the cross-shelf topographic slope (the “JEBAR” effect) to balance the enhanced intrusion. The downslope
flow also increases vortex stretching and decreases the thickness of the inertial boundary layer, resulting in a Kuroshio
that shifts closer to the shelf break. 相似文献
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Ocean Dynamics - The Gulf Stream (GS) transports a massive amount of heat northward to high latitudes and releases sensible and latent heat to the atmosphere, playing an important role in the North... 相似文献
7.
We present new results from the SINGG Hα survey of nearby galaxies, which show that starbursts have a lower fraction of diffuse, warm ionized gas than other star-forming galaxies. We discuss the possible causes of this effect, including a decrease in field-star contributions, absorption of ionizing radiation by dust, and the escape of ionizing radiation from the galaxies. 相似文献
8.
Hurricanes produce mixing and flow divergences (and convergences) that alter the upper-ocean heat content (OHC), which in turn affects the storm. Ocean observations under a hurricane are rare, making it difficult to validate forecast models. Past research have mainly focused on OHC-changes by vertical mixing and tacitly assumed that horizontal transports are slowly varying. Moreover, effects of coastal boundaries on ocean responses to hurricanes are generally omitted. This work uses satellite data to detect and verify forecast isopycnal motions under hurricane Wilma (Oct/16–26/2005) in the Caribbean Sea and the Gulf of Mexico. The model is then used to show that Wilma-induced convergences in northwestern Caribbean Sea produce increased Yucatan-Channel transport into the Gulf ahead of the storm, and the Yucatan–Loop Current front diverts most of this heat around the Loop. This response is distinct from that of an ocean without the Loop, for which warming is widespread north of the channel. These intricate ocean responses can impact hurricane predictions. 相似文献
9.
Baroclinic tidal flows and inundation processes in Cook Inlet, Alaska: numerical modeling and satellite observations 总被引：2，自引：0，他引：2
A wetting and drying (WAD) algorithm is implemented in a baroclinic three-dimensional ocean circulation model of Cook Inlet,
Alaska, where large tidal ranges (≈10 m) regularly expose extensive mudflats. The model includes tides and wind- and buoyancy-induced
flows. In the upper Inlet, the model successfully simulates large amplification of tides and propagation of fast (3 ∼ 4 m
s−1) tidal bores over shallow mudflats. The simulated return flows during ebb expose large areas (∼100 km2) of the mudflats. Medium-resolution (250- and 500-m) images obtained from the moderate resolution imaging spectroradiometer
(MODIS) instruments aboard the Terra and Aqua satellites were used to verify the model results by identifying the location,
extent, and temporal changes of the exposed mudflat regions. The results demonstrate the value of operational, medium-resolution
remote sensing data in evaluating the WAD model. Sensitivity tests show that WAD produces approximately 20% larger tidal amplitude
and 10% slower phase than the corresponding experiment without WAD. In the deep channel of the central Inlet, the confluence
of saline water of the lower Inlet with brackish water from rivers and melting ice from land around the upper Inlet produces
a salinity front. At the simulated front, strong vertical circulation cells and surface convergence and currents develop,
especially during the flood. The characteristics resemble those of “rip tides” often observed in this region. 相似文献
10.
Two-dimensional (cross-shelf and depth) circulation by downwelling wind in the presence of a prograding front (with isopycnals that slope in the same direction as the topographic slope) over a continental shelf is studied using high-resolution numerical experiments. The physical process of interest is the cross-shelf circulation produced by northeasterly monsoon winds acting on the Kuroshio front over the East China Sea outer shelf and shelfbreak where upwelling is often observed. However, a general problem is posed and solved by idealized numerical and analytical models. It is shown that upwelling is produced shoreward of the front. The upwelling is maintained by (1) a surface bulge of negative vorticity at the head of the front; (2) bottom offshore convergence beneath the front; and (3) in the case of a surface front that is thin relative to water depth, also by upwelling due to the vorticity sheet under the front. The near-coast downwelling produces intense mixing due to both upright and slant-wise convection in regions of positive potential vorticity. The analytical model shows that the size and on-shore propagating speed of the bulge are determined by the wind and its shape is governed by a nonlinear advection–dispersion equation which yields unchanging wave-form solutions. Successive bulges can detach from the front under a steady wind. Vertical circulation cells develop under the propagating bulges despite a stable stratification. These cells can have important consequences to vertical exchanges of tracers and water masses. 相似文献