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Delayed baroclinic response of the Antarctic circum-polar current to surface wind stress

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Science China Earth Sciences 2008年第7期51卷 1036-1043页

作者： YANG XiaoYi HUANG RuiXin WANG Jia WANG DongXiao LED South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Woods Hole Oceanographic Institution MA02543 USA NOAA Great Lakes Environmental Research Laboratory Ann ArborMI 48105USA

The Antarctic Circumpolar Current (ACC) responds to the surface windstress via two processes, i.e., the instant barotropic process and the delayed baroclinic process. This study focuses on the baroclinic instability mechanism in ACC, which was less reported in the literatures. Results show that the strengthening of surface zonal windstress causes the enhanced tilting of the isopycnal surface, leading to more intense baroclinic instability. Simultaneously, the mesoscale eddies resulting from the baro- clinic instability facilitate the transformation of mean potential energy to eddy energy, which causes the remarkable decrease of the ACC volume transport with the 2-year lag time. This delayed negative cor- relation between the ACC transport and the zonal windstress may account for the steadiness of the ACC transport during last two decades.

关键词： Antarctic Circumpolar Current zonal windstress baroclinic instability mesoscale eddy

Charney’s Model—the Renowned Prototype of baroclinic Instability—Is Barotropically Unstable As Well

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Advances in Atmospheric Sciences 2019年第7期36卷 733-752页

作者： Yuan-Bing ZHAO X.San LIANG School of Atmospheric Sciences Nanjing University of Information Science and TechnologyNanjing210044China School of Marine Sciences Nanjing University of Information Science and TechnologyNanjing210044China School of Mathematics and Statistics Nanjing University of Information Science and TechnologyNanjing210044China

The Charney model is reexamined using a new mathematical tool, the multiscale window transform(MWT), and the MWT-based localized multiscale energetics analysis developed by Liang and Robinson to deal with realistic geophysical fluid flow processes. Traditionally, though this model has been taken as a prototype of baroclinic instability, it actually undergoes a mixed one. While baroclinic instability explains the bottom-trapped feature of the perturbation, the second extreme center in the perturbation field can only be explained by a new barotropic instability when the Charney–Green number γ 1, which takes place throughout the fluid column, and is maximized at a height where its baroclinic counterpart stops functioning.The giving way of the baroclinic instability to a barotropic one at this height corresponds well to the rectification of the tilting found on the maps of perturbation velocity and pressure. Also established in this study is the relative importance of barotropic instability to baroclinic instability in terms of γ. When γ 1, barotropic instability is negligible and hence the system can be viewed as purely baroclinic;when γ 1, however, barotropic and baroclinic instabilities are of the same order;in fact, barotropic instability can be even stronger. The implication of these results has been discussed in linking them to real atmospheric processes.

关键词： Charney’s model multiscale window transform canonical transfer baroclinic instability barotropic instability

PSEUDOSPECTRAL-DIFFERENCE METHOD FOR baroclinic PRIMITIVE EQUATION AND ITS ERROR ESTIMATION

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Science China Mathematics 1992年第1期35卷 1-13页

作者：郭本瑜郑家栋 Shanghai University of Science and Technology Shanghai 201800 PRC Shanghai Institute of Computer Technology Shanghai 200040 PRC

In this paper, the pseudospectral-difference scheme is constructed for the baroclinicprimitive equation. The solution of such a scheme keeps energy unchanged. The strict errorestimation is given.

关键词： baroclinic primitive equation pseudospectal-difference scheme error estimation.

A three-dimensional baroclinic current model with wave effects

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Science China Chemistry 2001年第S1期44卷 92-98页

作者：丁平兴朱首贤孔亚珍 State Key Laboratory of Estuarine and Coastal Research East China Normal University Shanghai China

Waves can have a significant impact on nearshore currents. A three-dimensional baro-clinic current model including the influence of waves is presented for shallow water areas from Navier-Stokes equations. It has been found that the effects of waves on currents can be expressed in terms of the momentum flux by waves. The model uses non-orthogonal curvilinear coordinates in the horizontal directions and a Sigma coordinate in the vertical direction so that it can be more reasonably applied in estuarine and coastal regions.

关键词： waves and currents baroclinic model generalized curvilinear coordinate.

AN EXACT SOLUTION OF SUB-INERTIAL FREQUENCY baroclinic WAVES

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Chinese Journal of Oceanology and Limnology 1996年第1期14卷 79-82页

作者：江明顺方欣华 Physical Oceanography Institute Ocean University of Qingdao

By using a coordinate transformation, an exact solution of internal tides with sub-inertial frequency isobtained when the bottom slope is linear and the Vaisala frequency is constant. Accordingly thedispersion relations of free waves are presented. This solution is suitable for general coastal low-frequencybaroclinic waves with zero alongshore wavenumber.

关键词： baroclinic waves trapped waves internal tides

A 3-DIMENSIONAL baroclinic CIRCULATION MODEL OF THE TROPICAL AND NORTHERN PACIFIC

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Chinese Journal of Oceanology and Limnology 1997年第1期15卷 70-79页

作者：蔡怡李毓湘

A primitive equation 3-dimensional baroclinic ocean model without the rigid-lid approximation is described.The horizontal resolution is 2.5°×2°and the vertical variations of the velocity components are resolved by 6 layers. In order to increase the allowable integration time step which is constrained by stability requirements, the vertically integrated continuity equation is linearized and both the pressure gradient terms and the Coriolis terms in the momentum equations are finite-differenced semi-implicitly.The model is applied to simulate the circulation as well as the free surface elevation and temperature patterns in the tropical and northern Pacific Ocean in both summer and winter using the wind and temperature data at the 1000 mb pressure level as input to the .model. The computed results are in general consistent with observed patterns. In particular, it is shown that the positions of the meandering axis of the Kuroshio in summer and winter are markedly different.

关键词： baroclinic circulation model numerial solution tropical and northern Pacific

Vertical Structure of baroclinic Currents over Northern South China Sea Continental Slope

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Marine Science Bulletin 2001年第1期3卷 1-8页

作者： Qiu Zhang(邱章) South China Sea Institute of Oceanology the Chinese Academy of Sciences Guangzhou 510301

The 28.6 d time series of ADCP currents at 27 depth levels, (11,15,…,115m) which are obtained from a mooring station at the northern South China Sea continental slope, have been decomposed into barotropic and baroclinic components. The emphasis in this paper is on the analysis of the time series of baroclinic currents by means of several methods,such as the tidal harmonic analysis, the power spectra and the kinetic energy estimation.The major results are as follows: (1) In respect of the baroclinic currents, the values of several parameters first decrease and then increase with depth. These parameters include the temporal mean value of the cross-shelf component, the standard deviations, the amplitudes of K1 constituents, the mean eddy kinetic energy, as well as the significant peaks of the power spectra of the cross-shelf components. (2) The diurnal period of the baroclinic currents is dominant. The diumal tidal current rotates clockwise and the major axis of current ellipse is located along the directions of NW-SE. The vertical distribution of the phases of the diurnal constituent varies with the different water layers. Around the 67m depth level, the phase changes very much.At those layers far away from the 67m depth level, the vertical distribution of the phase is relatively stable, but with opposite phases in the upper and lower water layers. For the upper layers between the surface and 67m,the phases are around 300°; for the lower layers between 67m and 115m, the phases are around 120° .(3) The mean eddy kinetic energy of the baroclinic current is quite large, accounting for 41% of the mean kinetic energy of the measured currents. The cross-shelf component is larger than the along-shelf one. The two baroclinic current components correspond to the major and minor axes of the current ellipse of the diurnal constituent respectively. (4) The power spectra of the baroclinic currents show a singnificant period of about 24h, with 23.6h at both 19m and 99m and 24.4h at 55m. The vertical distributions of the signific

关键词： Northern South China Sea, barotropic current, baroclinic current

Atmopheric Nonlinear Rossby Elliptic Cosinusoidal and Solitary Waves in a baroclinic Model

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Chinese Science Bulletin 1993年第7期38卷 572-576页

作者：何建中 Nanjing Institute of Meteorology Nanjing 210044 PRC

Under a semi-geostrophic approximation, the equations goyeming motions in a baroclinic atmosphere read in which （2） is the condition of geostrophic balance; N, the Brunt-Visl frequency characterizing stratification; ρ0, the motionless air density; φ, ρ’/ρ0, with ρ’ denoting the pressure deviation from that of motionless air; ξ（0）, the geostrophic vorticity; ▽2, the twodimensional Laplace operator; and the othees are of usual implications in

关键词： baroclinic semi-geostrophic nonlinear Rossby wave.

Effects of surface drag on low-level frontogenesis within baroclinic waves

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Science China Earth Sciences 2007年第2期50卷 306-319页

作者： ZHANG Yi TAN ZheMin Key Laboratory of Mesoscale Severe Weather of Ministry of Education and Department of Atmospheric SciencesNanjing Univer-sityNanjing 210093China

Using a three-dimensional nonhydrostatic mesoscale numerical model (MM5), the evolution and structures of baroclinic waves with and without surface drag in case of dry and moist atmosphere are simulated, with special emphases on the effects of surface drag on the low-level frontal structure and frontogenesis. There are two different effects of surface drag on the low-level frontogenesis in the dry case. On one hand, the surface drag weakens the low-level frontogenesis and less inclined to develop the baroclinic wave due to the dissipation. But on the other hand, the surface drag induces a strong ageostrophic flow, which prolongs the low-level frontogenesis and finally leads to the enhancement of cold front. Compared with the no surface drag case, the surface drag increases the frontal slope espe- cially in the boundary layer, where the front is almost vertical to the surface, and then enhances the prefrontal vertical motion. All these conclusions expanded the analytical theory of Tan and Wu (1990). In the moist atmosphere, the influence of surface drag on frontal rainbands is also obvious. The surface drag weakens the convection, and reduces the energy dissipation near the surface when the initial relative humidity is relatively weak. At this time, the confluence induced post-frontal updrafts moves across the cold front and reinforces the prefrontal convection, which is beneficial to the maintenance of the rainband in cold sector. Given the enhancement of relative humidity, the moist convection domi- nates the low-level frontogenesis while the retardation of surface drag on energy dissipation is not obvious, therefore the effects of surface drag on the low-level frontogenesis and precipitation are re- duced.

关键词： surface drag baroclinic wave frontogenesis diabatic heating frontal rainband