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使用斯克里普斯海洋研究所（SIO）整编的海洋上层（海表至400m）热储量资料，研究了热带太平洋上层热力状况季节变化的正压特征，指出与SST的分布不同，热储量在北纬5°N～10°N之间有一东西贯穿整个太平洋的带状热储量低值区，其季节变化率的分布特征分为两种，一是11月至2月为代表的“北半球冬季型”和5～8月的“北半球夏季型”，3月、4月和9月、10月为过渡阶段. 北半球10°N和2°N的季节变率的时间变化反位相，南半球的10°S、2°S?其季节变率随时间变化的位相则比较一致且与沿10°N位相大致相反. 东太平洋季节变化明显早于中、西太平洋，具有明显自东向西传播的特征. 10°S与10°N之间东、西太平洋的季节变率随时间的演变也基本上呈现反位相特征. 相似文献
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利用“延平2号”科学调查船于2005年6月下旬在台湾海峡中部（119．2°E,24．3°N）实施的定点连续观测资料,研究了夏季风期间障碍层的日变化过程及其局地反馈特征．障碍层开始形成时,由于非太阳辐射局限于上混合层,而太阳辐射可以穿透混合层底直至温跃层,导致障碍层内累积了最多热能,形成逆温层．随着障碍层内部热量的不断累积,障碍层与上混合层之间的热交换过程逐渐增强,上混合层显著增暖。此外,障碍层对应浮力频率极小值区,具有较弱的层结稳定性;针对海气通量的分析表明障碍层造成了显著的局地感热、潜热通量异常．进一步分析表明,海表风搅拌产生的湍动能在向下传输过程中,次盐跃层和温跃层构成了两个界面,大部分湍动能被较浅的盐度层结阻挡,限制在混合层以上,部分穿透混合层底的湍动能再次被温跃层阻挡,障碍层对应湍动能的薄弱区． 相似文献
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利用15年（1993～2007年）月平均的海表面高度（SSH）异常资料,分析了北太平洋海表面高度的年际变化的时空结构,并研究了热通量和风应力两个因子对其的强迫作用.结果表明,北太平洋年际时间尺度SSH变化的大值区在黑潮延伸区和西太平洋暖池区.EOF分解第一模态的空间结构沿纬向呈带状分布,第二模态为沿经向呈带状分布.热通量强迫作用在中纬度的东北太平洋可以解释SSH年际变化40%以上.风应力对SSH的作用包括正压和斜压两个方面.正压Sverdrup平衡模型模拟的SSH年际变化较弱,仅能解释高纬度副极地环流西部的20%~40%.由大尺度风应力强迫的第一阶斜压Rossby波模型可以解释热带地区的20%~60%,中纬度中部的20%~40%,以及阿拉斯加环流东部和副极地环流西部的20%~60%.风应力强迫的一阶斜压Rossby波模型对SSH的强迫机理又可分为局地风应力强迫和西传Rossby波作用.其中,风应力的局地强迫作用（Ekman抽吸）在东北太平洋、白令海以及热带中部有显著的预报技巧,可以解释SSH年际变异的40%以上.Rossby波的传播作用在中纬度海域的副热带环流中西部和夏威夷岛以东起着重要作用,可解释20%~60%. 相似文献
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粤东沿岸上升流对2006年夏季台风响应 总被引：2，自引：0，他引：2
通过在粤东沿岸进行的大面走航CTD观测,特别是座底式的海床基测流资料,比较详细的探讨了台风过境对粤东沿岸上升流系统的影响.研究结果表明：南海夏季风驱动的东北向地转流在汕头附近存在显著的近海底向岸分量,与上层的离岸埃克曼平流共同构成了粤东近岸的典型上升流系统.进一步的分析表明粤东沿岸上升流系统对台风强度及其入侵路径比较敏感.当台风入侵路径位于上升流系统以北时（如0604号台风碧利斯和0605号台风凯米）,在台风过境初期,局地西南风的异常增大使得向岸流显著增强,即上升流增强;在台风过境期及后期,无论是由于局地风场过强导致的海洋受迫响应（0604号台风碧利斯）,还是中度台风诱发的惯性振荡（0605号台风凯米）,都不利于维持一个稳定的、持续的上升流系统.当台风从上升流系统以南入侵时（如0606号台风派比安）,有利于上升流产生的西南风被东北风取代,风驱向岸的埃克曼平流效应以及质量守恒使得海洋中、下层为离岸流,上层为向岸流,粤东沿岸传统的上升流结构遭到彻底颠覆;当台风过境后,典型的上升流结构会在1～2d内回复. 相似文献
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利用绿洲和戈壁近地面层湍流实验资料对比研究表明,在不稳定层结条件下,绿洲和戈壁中温度归一化方差满足φθ（z／Λ）=αθ（-z／θ）^-1/3,而绿洲湿度和CO2归一化方差都满足φs（z／Λ）=αs（1-βsz／Λ）^-1/3;受平流影响,绿洲温度归一化方差量值较大,而戈壁CO2方差相对M-O函数关系有一定程度的偏离,湿度方差则完全背离了方差M-O关系;对上述结果分析表明,平流条件下,湿度方差满足关系式σsm^2=D^2σsA^2＋σsB^2;其方差M-O关系由平流输送标量方差值的相对大小所决定。对于湿度和CO2等标量,如果平流输送的标量方差比局地标量方差大得多,则该标量方差观测值就会背离方差M-O关系,当平流输送的标量方差接近或小于局地标量方差时,标量方差观测值基本满足方差M—O关系。 相似文献
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采用一个开边界海盆尺度环流模式研究人为CO2在北太平洋的吸收和分布，并与闭边界模式的模拟结果进行了比较.模拟结果表明，西北太平洋和赤道东太平洋是两个重要的人为CO2汇.使用较大的等密度面扩散系数使得西北太平洋人为CO2通量增大，而赤道海区通量减小（RUN2）.与闭边界模式相比，开边界模式中该两个区域的人为CO2通量都增加了.1800～1997年间，北太平洋共吸收人为CO2 2375GtC(1Gt=1×1015 g, RUN1).副极地海区是人为CO2的一个重要输出区，能输出人为CO2吸收量的38％～54％，而20°N～30°N海区是人为CO2的一个重要贮存区，占整个北太平洋的24％.开边界对于10°N以南太平洋吸收和贮存人为CO2有很大影响.与基于观测资料的估计相比，虽然模式低估了西北太平洋的人为CO2的穿透，高估了东北太平洋的人为CO2的穿透，但总的说来，模式比较好地估计了人为CO2在北太平洋的贮存. 相似文献
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利用美国国家环境预测中心（NCEP）和联合环境数据分析中心（JEDAC）资料，分别定义了表征海洋和大气变异的风场涡度指数和温度场指数，对热带太平洋海域的极值曲面上的温度距平、850 hPa风应力旋度进行了分析.结果显示，大气对海洋热力强迫的响应主要是Gill型，而大气又可以通过风应力旋度造成的Ekman抽吸作用来影响海洋，这种海气相互作用影响着ENSO循环的发展.通过简单的统计分析，解释了二者在ENSO循环之中所起的作用，并从资料中验证了El Nio事件具有3～4年的循环周期.这在一定程度上支持了ENSO的时滞振荡子和自然振荡子理论. 相似文献
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跨越中、印、缅三国交界的喜马拉雅“东构造结”地区（92°E～97°E，26°N～30°N）有一半以上的面积尚没有重力测点，是重力数据空白区,故无法直接研究其重力场特征与深部地壳结构（构造）.本文应用卫星重力异常资料作为近似空间重力异常，经计算给出的布格重力异常，其特征与该地区的地形高程呈很好的镜像相关.据此得到该区不同方位的3个地壳深部结构剖面.重力异常反演求得青藏高原地壳厚度>70 km；喜马拉雅造山带为55 km左右；布拉马普特拉河谷盆地为33～35 km；那加山山脉地区为40～45 km，即呈现出3个不同构造单元的展布.同时求得“东构造结"区由高密度的刚性物质构成，在印度洋板块的碰撞、挤压作用下呈向北运移，并插入青藏高原东缘.基于这样的构造格局和深层动力过程，导致了青藏高原东南缘和东北缘的强烈构造运动，大、小地震的频频发生和矿产资源的聚集. 相似文献
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利用中等复杂程度热带大气和海洋模式研究了热带太平洋和大西洋SST通过风应力桥梁的相互作用.利用1958～1998年NCEP分析的海表面温度场（SST）强迫大气模式得到的表面风应力与NCEP分析的同期热通量共同驱动海洋模式，作为控制试验；和控制试验平行，但强迫大气模式的SST在某一海盆取为多年气候平均值的试验作为敏感性试验；比较控制试验与敏感性试验模拟，则可反映风应力桥梁作用下热带某海盆SST异常对其他海盆的影响.结果表明，热带某一海盆SST暖（冷）异常总是引起局地海盆表面西部西（东）风异常和东部东（西）风异常；热带太平洋SST暖（冷）异常导致的该海盆东部表面东（西）风异常可以扩展到热带大西洋，从而导致热带大西洋SST冷（暖）异常；热带大西洋SST暖（冷）异常导致的该海盆西部表面西（东）风异常可以扩展到热带太平洋，从而导致热带太平洋SST暖（冷）异常. 相似文献
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Abstract A nonlinear Stommel model of the ocean circulation on the beta plane, driven by a time periodic wind stress, is investigated in order to study symmetry properties of the observed time-mean ocean gyres. Due to the presence of vorticity advection terms the model will have a steady or rectified response to fluctuating wind fields. In this paper a small inverse Ekman number, “the small beta regime”, is considered. It is demonstrated that for this case all qualitative features of the residual circulation, obtained numerically by Veronis (1970). are reproduced in an analytical way. They include the dipole character of the gyre, its maximum symmetry breaking around the north-south axis for intermediate Reynolds numbers, measuring the ratio of vorticity forcing and dissipation, and the maximum residual response for intermediate forcing frequencies. 相似文献
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Nisha Kurian Matthieu Lengaigne Gopalakrishna Venkata Vissa Jerome Vialard Stephane Pous Anne-Charlotte Peter Fabien Durand Shweta Naik 《Ocean Dynamics》2013,63(4):329-346
Active and break phases of the Indian summer monsoon are associated with sea surface temperature (SST) fluctuations at 30–90 days timescale in the Arabian Sea and Bay of Bengal. Mechanisms responsible for basin-scale intraseasonal SST variations have previously been discussed, but the maxima of SST variability are actually located in three specific offshore regions: the South-Eastern Arabian Sea (SEAS), the Southern Tip of India (STI) and the North-Western Bay of Bengal (NWBoB). In the present study, we use an eddy-permitting 0.25° regional ocean model to investigate mechanisms of this offshore intraseasonal SST variability. Modelled climatological mixed layer and upper thermocline depth are in very good agreement with estimates from three repeated expendable bathythermograph transects perpendicular to the Indian Coast. The model intraseasonal forcing and SST variability agree well with observed estimates, although modelled intraseasonal offshore SST amplitude is undere-stimated by 20–30 %. Our analysis reveals that surface heat flux variations drive a large part of the intraseasonal SST variations along the Indian coastline while oceanic processes have contrasted contributions depending of the region considered. In the SEAS, this contribution is very small because intraseasonal wind variations are essentially cross-shore, and thus not associated with significant upwelling intraseasonal fluctuations. In the STI, vertical advection associated with Ekman pumping contributes to ～30 % of the SST fluctuations. In the NWBoB, vertical mixing diminishes the SST variations driven by the atmospheric heat flux perturbations by 40 %. Simple slab ocean model integrations show that the amplitude of these intraseasonal SST signals is not very sensitive to the heat flux dataset used, but more sensitive to mixed layer depth. 相似文献
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《Marine pollution bulletin》2011,62(7-12):432-448
An outstanding characteristic of New Caledonia upwelling is that most events appear limited to the southern half of the western barrier reef. This north–south difference cannot be explained by alongshore variability of the projected wind stress and no strong evidence for alternative explanations has been proposed. A major objective of this paper is to provide the first dynamical analysis of New Caledonia upwelling and its regional environment, based on numerical simulations. Coastal upwelling around New Caledonia is shown to be modulated by a system of geostrophic currents interacting with the island mass. Upwelling velocities are weaker than expected from the two-dimensional Ekman theory, as Ekman divergence is balanced by “coastal geostrophic convergence”. The cooling effect of upwelling is also attenuated by alongshore transport of warm water by the Alis current, reminiscent of the Leeuwin current off Western Australia. Nevertheless, coastal upwelling can locally modify the large-scale surface water heat budget, dominated by meridional advection warming and surface cooling. The upwelled waters appear to be mostly of western origin and are transported below the surface by the Subtropical Counter Current before upwelling off New Caledonia. This appears in sharp contrast with the eastern barrier reef where the general warming by meridional advection of tropical surface waters is accentuated by the vigorous western boundary type Vauban current. 相似文献
14.
Achim Wirth 《Ocean Dynamics》2009,59(4):551-563
Results from numerical simulations of idealised, 2.5-dimensional Boussinesq, gravity currents on an inclined plane in a rotating
frame are used to determine the qualitative and quantitative characteristics of such currents. The current is initially geostrophically
adjusted. The Richardson number is varied between different experiments. The results demonstrate that the gravity current
has a two-part structure consisting of: (1) the vein, the thick part that is governed by geostrophic dynamics with an Ekman
layer at its bottom, and (2) a thin friction layer at the downslope side of the vein, the thin part of the gravity current.
Water from the vein detrains into the friction layer via the bottom Ekman layer. A self consistent picture of the dynamics
of a gravity current is obtained and some of the large-scale characteristics of a gravity current can be analytically calculated,
for small Reynolds number flow, using linear Ekman layer theory. The evolution of the gravity current is shown to be governed
by bottom friction. A minimal model for the vein dynamics, based on the heat equation, is derived and compares very well to
the solutions of the 2.5-dimensional Boussinesq simulations. The heat equation is linear for a linear (Rayleigh) friction
law and non-linear for a quadratic drag law. I demonstrate that the thickness of a gravity current cannot be modelled by a
local parameterisation when bottom friction is relevant. The difference between the vein and the gravity current is of paramount
importance as simplified (streamtube) models should model the dynamics of the vein rather than the dynamics of the total gravity
current. In basin-wide numerical models of the ocean dynamics the friction layer has to be resolved to correctly represent
gravity currents and, thus, the ocean dynamics. 相似文献
15.
对多震相走时层析成像方法进行改进和优化, 使用朝鲜半岛陆地和近海的地震记录, 对朝鲜半岛南部(345°N～39°N，125°E～130°E)进行地震波走时反演， 获得了本研究区的三维速度结构成像结果.分析了沉积层、基底、上地壳、康腊面、下地壳和莫霍面的特征.研究了不同地质区的深部结构的主要差别、主要断裂特征、 海陆交界的地壳特征等.可以发现京畿山地与沃川褶皱带、太白山褶皱带、临津江褶皱带深部结构的差异尤为明显. 相似文献
16.
Steven L. Morey Mark A. Bourassa Dmitry S. Dukhovskoy James J. O’Brien 《Ocean Dynamics》2006,56(5-6):594-606
A coupled ocean and boundary layer flux numerical modeling system is used to study the upper ocean response to surface heat
and momentum fluxes associated with a major hurricane, namely, Hurricane Dennis (July 2005) in the Gulf of Mexico. A suite
of experiments is run using this modeling system, constructed by coupling a Navy Coastal Ocean Model simulation of the Gulf
of Mexico to an atmospheric flux model. The modeling system is forced by wind fields produced from satellite scatterometer
and atmospheric model wind data, and by numerical weather prediction air temperature data. The experiments are initialized
from a data assimilative hindcast model run and then forced by surface fluxes with no assimilation for the time during which
Hurricane Dennis impacted the region. Four experiments are run to aid in the analysis: one is forced by heat and momentum
fluxes, one by only momentum fluxes, one by only heat fluxes, and one with no surface forcing. An equation describing the
change in the upper ocean hurricane heat potential due to the storm is developed. Analysis of the model results show that
surface heat fluxes are primarily responsible for widespread reduction (0.5°–1.5°C) of sea surface temperature over the inner
West Florida Shelf 100–300 km away from the storm center. Momentum fluxes are responsible for stronger surface cooling (2°C)
near the center of the storm. The upper ocean heat loss near the storm center of more than 200 MJ/m2 is primarily due to the vertical flux of thermal energy between the surface layer and deep ocean. Heat loss to the atmosphere
during the storm’s passage is approximately 100–150 MJ/m2. The upper ocean cooling is enhanced where the preexisting mixed layer is shallow, e.g., within a cyclonic circulation feature,
although the heat flux to the atmosphere in these locations is markedly reduced. 相似文献
17.
Synoptic sea surface temperature anomalies (SSTAs) were determined as a result of separation of time scales smaller than 183 days. The SSTAs were investigated using daily data of ocean weather station “C” (52.75°N; 35.5°W) from 1 January 1976 to 31 December 1980 (1827 days). There were 47 positive and 50 negative significant SSTAs (lifetime longer than 3 days, absolute value greater than 0.10 °C) with four main intervals of the lifetime repetitions: 1. 4–7 days (45% of all cases), 2. 9–13 days (20-25%), 3. 14–18 days (10-15%), and 4. 21–30 days (10-15%) and with a magnitude 1.5-2.0 °C. An upper layer balance model based on equations for temperature, salinity, mechanical energy (with advanced parametrization), state (density), and drift currents was used to simulate SSTA. The original method of modelling taking into account the mean observed temperature profiles proved to be very stable. The model SSTAs are in a good agreement with the observed amplitudes and phases of synoptic SSTAs during all 5 years. Surface heat flux anomalies are the main source of SSTAs. The influence of anomalous drift heat advection is about 30-50% of the SSTA, and the influence of salinity anomalies is about 10-25% and less. The influence of a large-scale ocean front was isolated only once in February-April 1978 during all 5 years. Synoptic SSTAs develop just in the upper half of the homogeneous layer at each winter. We suggest that there are two main causes of such active sublayer formation: 1. surface heat flux in the warm sectors of cyclones and 2. predominant heat transport by ocean currents from the south. All frequency functions of the ocean temperature synoptic response to heat and momentum surface fluxes are of integral character (red noise), though there is strong resonance with 20-days period of wind-driven horizontal heat advection with mixed layer temperature; there are some other peculiarities on the time scales from 5.5 to 13 days. Observed and modelled frequency functions seem to be in good agreement. 相似文献
18.
用北半球陆地上48个地面电离层垂测站资料，以及国际参考电离层IRI 90模式，考察1985年1月6～7日F2层电子密度最大值日变化的纬度剖面和经度效应. 结果表明，在亚洲地区的20°N～30°N内，F2层赤道异常“喷泉效应”产生的NmF2“北驼峰”最高，其最大值出现在中午，或稍迟时间. 30°N ～50°N区域内，NmF2的白天峰值幅度逐渐下降，峰值时间移至午前约10:00 LT. 更高纬度(50°N～62°N )台站上，中午前后NmF2出现双峰，傍晚有谷值，夜间又再次抬升. 欧、美地区的低纬台站很少，但借助IRI 90模式分析可发现，在270°E经圈上，“喷泉效应”造成的“北驼峰”幅度最小，而且随纬度增大时，NmF2白天幅度下降也不明显，即纬度剖面的经度效应非常显著. 对中国、日本地区台站资料的小范围经度差异分析表明，在驼峰区的90°E～140°E内，各站NmF2无明显差别；但在中纬地区30°N～50°N内，中国西部上空NmF2白天变化幅度较大，且较为陡直，而中国东部和日本台站上空则相对平缓. 相似文献
19.
The circulation of the Southern Ocean is studied in the eddy-resolving model POP (Parallel Ocean Program) by an analysis
of zonally integrated balances. The TEM formalism (Transformed Eulerian Mean) is extended to include topography and continental
boundaries, thus deviations from a zonally integrated state involve transient and standing eddies. The meridional circulation
is presented in terms of the Eulerian, eddy-induced, and residual streamfunctions. It is shown that the splitting of the meridional
circulation into Ekman and geostrophic transports and the component induced by subgrid and Reynolds stresses is identical
to a particular form of the zonally integrated balance of zonal momentum. In this balance, the eddy-induced streamfunctions
represent the interfacial form stresses by transient and standing eddies and the residual streamfunction represents the acceleration
of the zonal current by density fluxes in a zonally integrated frame. The latter acceleration term is directly related to
the surface flux of density and interior fluxes due to the resolved and unresolved eddies. The eddy-induced circulation is
extremely vigorous in POP. In the upper ocean a shallow circulation, reversed in comparison to the Deacon cell and mainly
due to standing eddies, appears to the north of Drake Passage latitudes, and in the Drake Passage belt of latitudes a deep-reaching
cell is induced by transient eddies. In the resulting residual circulation the Deacon cell is largely cancelled and the residual
advection of the zonal mean potential density is balanced by diapycnal eddy and subgrid fluxes which are strong in the upper
few hundred meters but small in the ocean interior. The balance of zonal momentum is consistent with other eddy-resolving
models; a new aspect is the clear identification of density effects in the zonally integrated balance. We show that the wind
stress and the stress induced by the residual circulation drive the eastward current, whereas both eddy species result in
a braking. Finally, we extend the Johnson–Bryden model of zonal transport to incorporate all relevant terms from the zonal
momentum balance. It is shown that wind stress and induction by the residual circulation carry an eastward transport while
bottom form stress and the stress induced by standing eddies yield westward components of transport.
Received: 26 June 2001 / Accepted: 2 November 2001 相似文献