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2.
Aminath S. Rasheed 《大气与海洋》2014,52(2):155-168
The secular trends for local tidal datums, tide ranges, and tidal harmonic constituents at 13 tidal gauge stations located along the coast of Japan were analyzed in this study. The general trends for mean higher high water (MHHW), mean high water (MHW), diurnal tide range (DTR), mean tide range (MTR), and relative mean sea level (RMSL) were positive, and for mean lower low water (MLLW) and mean low water (MLW) the trends were negative. The variation patterns were largest at Kushiro and Ofunato stations, both located in the open waters of the North Pacific Ocean. The tidal datums and tide ranges remained fairly stable at the Hakodate station, and an opposite trend was observed at the Maisaka station. The analysis of tidal harmonic constituents revealed a less pronounced pattern. The most distinct trend was observed for the M2 amplitude, which appears to be negative at a majority of the stations. The largest decrease in the M2 amplitude was observed at Kushimoto and Mera stations, also located in the open waters of the North Pacific Ocean. The negative trend is attributed to decreasing water depths at these stations, owing to small-scale local processes. 相似文献
3.
Field experimental materials on the sea current measurements, carried out by the Sakhalin Research Institute for Fishery and Oceanography in September–December 2004 near the Sakhalin southeastern coast, are analyzed. The experiment included the installation of two coastal and one more remote autonomous buoy stations. The tidal flows in this region, unlike those on the northeastern shelf of the island, are relatively small and do not play a significant role in the dynamics of the coastal zone. The character of currents at coastal stations is determined primarily by their response to the wind effect. In particular, significant water temperature falls of 6–8°C, observed from 2–3 days to a week, are indicative of coastal upwelling induced by the wind. During the passage of a deep cyclone that caused a storm wave 1 m high, the flow velocity at coastal stations increased up to 1.5 knots. At a more remote station, in the region of Cape Svobodnyi, the flow character was determined by the East Sakhalin Current, whose autumn intensification was observed in the second ten-day period of October. It manifested itself in a sharp intensification of the flow, directed southward and southeastward throughout the entire water column, which practically was not pronounced at the coastal stations. 相似文献
4.
Abstract A non‐linear response in current‐meter compasses is examined in terms of its effect on the measured residual current. It is shown that, even for a compass response within typical manufacturers’ specifications, the induced errors are important for regions where the residual speed is less than about 10% of the peak tidal current. In an M2 current, the non‐linearity also induces an M4 signal, but this is not sufficiently large to be easily detected by tidal analyses. 相似文献
5.
P. Ya. Tishchenko V. B. Lobanov T. A. Gulenko A. P. Nedashkovskii O. S. Popov S. G. Sagalaev P. P. Tishchenko R. V. Chichkin 《Russian Meteorology and Hydrology》2012,37(11-12):775-782
During the hydrological survey from November 4 to 9, 2009, the underway measurements of pH, temperature, and salinity of the surface water in the Peter the Great Bay were carried out using the cell without the liquid junction in the running system. Using the measurement data, the partial pressure of carbon dioxide (pCO2) was computed which was below its atmospheric value and varied from 290 to 360μatm. Thus, during the period under study, the surface water of the bay forms the runoff for the atmospheric carbon dioxide. The minimum values of pCO2 are associated with the warm stream entering the bay from the southwestern part of the open sea. The maximum values of pCO2 are associated with the local upwelling of bottom waters. It is suggested that the horizontal convection caused by the nonuniform cooling of coastal water in the autumn forms the revealed mesoscale dynamic structures. 相似文献
6.
Abstract A two‐dimensional, hydrostatic numerical model of the tides in Knight Inlet is compared with observations of velocity and density obtained from three cyclesonde moorings. The observations from a fourth cyclesonde mooring were used to provide boundary data at the open end of the model. The time period in the fjord that the model simulates was a period of high, freshwater runoff, so that the fjord had a distinct, surface layer. The use of high, vertical resolution was avoided by attaching a homogeneous, fresh, surface layer to the top of the model. The density equation was linearized about a mean, fixed density field, and the mixing of density was not allowed. The model reproduces the semidiurnal (M2, S2 and N2) and diurnal (K1 and O1) velocity and density signals in the inlet. The shallow‐water constituents (M4 and MK3) are reproduced even though the density equation has been linearized. The fortnightly constituent (MSf) is poorly simulated. When the advection terms in the momentum equation are set to zero, the basic features of the semidiurnal and diurnal constituents are still reproduced, but the shallow‐water constituents are poorly simulated. The energy flux along the inlet of the M2 internal tide is insensitive to the advective terms in the momentum equation. The total rate of dissipation of M2 energy is similar to the energy flux in the M2 internal tide near the sill, which implies that, according to the model, most of the energy removed from the barotropic tide is fed into the internal tide. The majority of the energy in the M2 internal tide is dissipated close to the sill of the inlet, but enough of the energy makes its way to the head of the inlet to reflect and set up a recognizable standing wave pattern. 相似文献
7.
Martin Claussen 《Boundary-Layer Meteorology》1991,54(1-2):1-27
Micro-scale turbulent transport processes over the marginal ice zone have been studied by use of a two-dimensional numerical model. It has been found that internal boundary layers (IBLs) of horizontal mean velocity, temperature, and specific humidity reveal a near field and a far field. In the near field, the change in surface roughness dominates the height and growth rate of a velocity IBL. The change in surface heat flux governs the near field of a temperature and humidity IBL. In the far field, approximately x/¦L
*2
¦ ~ 20, where L
*2 is the downstream Obukhov length, the downstream stratification more and more influences the growth rate of IBLs basically by modifying the eddy viscosity.Above more complex terrain consisting of an ensemble of ice strips and leads, a merging height h
M
develops, below which the horizontal variability of the surface modification is clearly observed; h
M
varies with the length scale L of surface modification approximately in proportion to h
M
/L ~ 1/20 – 1/10, as a rule of thumb. Above the merging height, an enveloping IBL exists, whose growth depends on the ice cover, i.e., on the integral of surface modification, but changes very little with L.Local advection of momentum, heat, and moisture clearly affects the local surface heat fluxes. Sensible and latent heat fluxes are found to show also a near and far field. However, if areally averaged surface fluxes are to be deduced from grid-averaged flow variables, then details of local advection can be neglected to a reasonably good approximation. 相似文献
8.
《大气与海洋》2012,50(4):59-76
Acoustic Doppler Current Profiler (ADCP) measurements of the velocity structure in the thermocline in Luzon Strait are presented. The statistics for current, vertical variation of the inertia-gravity waveband, parametric subharmonic instability (PSI), and current shear are analyzed. It was found that 1) barotropic flow primarily consists of a nearly circular mixed tide. Diurnal tides are strongest and show smooth variance with a fortnightly spring-neap cycle, indicative of the astronomical tide-generating force. However, the semi-diurnal band power exhibits a high-frequency oscillation as a result of non-linear interactions. The high-frequency band power with high values during the spring tide oscillates with the tidal cycle. Near-inertial wave motions showing random variance may be caused by changes in the wind forcing at the sea surface or by random forcing. 2) Baroclinic velocities exhibit strong shear structure. The observed large changes in the amplitude of the baroclinic velocity and the limited vertical extent of the high-velocity cores may be interpreted as internal wave beams that pass through the observed water column. Semi-diurnal tides are dominant in the baroclinic velocity. Kinetic energy spectra also revealed that additional peaks were centred at sum-tidal-inertial interaction frequencies (such as M2 ?+?f) and difference-interaction frequencies (such as M2 ???f). The spectral exponent of the baroclinic velocity is ω?α (1?<?α?<?3). 3) Strong non-linear interactions among internal waves exist, and the semi-diurnal (M2) component plays a key role in these interactions. Bicoherence analysis showed that M2/2 waves were non-linearly coupled with the dominant M 2 internal tide. 4) The polarization relations were used to diagnose observational internal tidal motions. Diurnal waves propagate to the east-northeast, and the semi-diurnal–diurnal waves propagate westward. In the case of diurnal tides, the minor to major axis ratio is different from the expected value of f/ωK 1 because of the deviation of inclinations, whereas, for semi-diurnal tides, it is close to the expected value of f/ω M2 at depths from 30 to 150 m. RÉSUMÉ?[Traduit par la rédaction] Nous présentons les mesures de la structure des vitesses dans la thermocline faites par profileur de courant à effet Doppler (ADCP) dans le détroit de Luçon. Nous analysons les statistiques sur le courant, la variation verticale de la gamme d'ondes d'inertie-gravité, l'instabilité subharmonique paramétrique (PSI) et le cisaillement du courant. Il ressort que 1) l’écoulement barotrope consiste principalement en une marée mixte presque circulaire. Les marées diurnes sont les plus fortes et présentent une variance régulière dans un cycle vives-eaux mortes-eaux de deux semaines qui révèle la nature astronomique de la force qui produit les marées. Cependant, la puissance de bande semi-diurne affiche une oscillation de haute fréquence causée par des interactions non linéaires. La puissance de bande de haute fréquence avec des valeurs élevées durant les vives-eaux oscille avec le cycle des marées. Les mouvements des ondes quasi inertielles affichant une variance aléatoire peuvent être dus à des variations dans le forçage par le vent à la surface de la mer ou à un forçage aléatoire. 2) Les vitesses baroclines exhibent une structure fortement cisaillée. Les changements marqués observés dans l'amplitude des vitesses baroclines et l'extension verticale limitée des c?urs de vitesse élevée peuvent être interprétés comme des faisceaux d'ondes internes qui traversent la colonne d'eau observée. Les marées semi-diurnes sont dominantes dans les vitesses baroclines. Les spectres d’énergie cinétique ont aussi révélé que des crêtes additionnelles étaient centrées aux fréquences d'interaction cumulative marée-inertie (comme à M2 ?+?f) et aux fréquences d'interaction différentielle (comme à M2 ???f). L'exposant spectral de la vitesse barocline est ω?α (1?<?α?<?3). 3) Il existe de fortes interactions non linéaires entre les ondes internes et la semi-diurne (M2) joue un rôle clé dans ces interactions. L'analyse de bicohérence a montré que les ondes M2/2 étaient non-linéairement couplées avec la marée interne dominante M2 . 4) Nous avons utilisé les relations de polarisation pour diagnostiquer les mouvements de marée internes déduits des observations. Les ondes diurnes se propagent vers l'est-nord-est et les ondes semi-diurnes se propagent vers l'ouest. Dans le cas des marées diurnes, le rapport de l'axe secondaire à l'axe principal diffère de la valeur attendue (f/ωK 1 ) à cause de l’écart des inclinaisons alors que pour les marées semi-diurnes, il est proche de la valeur attendue (f/ω M2 ) à des profondeurs de 30 à 150 m. 相似文献
9.
K.F. Drinkwater 《大气与海洋》2013,51(2):252-266
Abstract The vertical structures of the mean and tidal flows in Hudson Strait are described from moored current‐meter data collected during an 8‐week period in August to October of 1982. The residual flow in the strongly stratified waters off Quebec is directed along the Strait to the southeast, is highly baroclinic and is concentrated near shore (within an offshore length scale of approximately an internal Rossby radius). Maximum mean speeds of 0.3 m s?1 were observed near‐surface (30 m). In the weakly stratified waters on the northern side of the Strait along Baffin Island the mean flow is northwestward. The maximum speeds are 0.1 m s?1 near‐surface (30 m) and the current amplitudes decrease to 0.05 m s?1 at 100 m. The mean southeastward transport is estimated to be 0.93 ±0.23 × 106 m3 s?1 with a northwestward transport of 0.82 ± 0.24 × 106 m3 s?1. Over most of the Strait the across‐channel residual currents are directed towards the Quebec shore with velocities ranging from 0.02 to 0.1 ms?1. Current variability is dominated by the tides, the M2 being the major tidal constituent. In the vicinity of the mooring the M2 tide is primarily barotropic, progressive in nature, and has along‐channel current amplitudes varying across the Strait from 0.20 to 0.45 m s?1. Observed differences in tidal sea‐level elevations across the Strait can be accounted for by the cross‐channel variations characteristic of Kelvin waves. 相似文献
10.
Abstract A modified response analysis in the form of an orthotide parametrization is used to derive major semi‐diurnal and diurnal tidal constituents over the Newfoundland and Scotian Shelves from TOPEX/POSEIDON altimeter data. The orthotide formulation simultaneously solves for eight major semi‐diurnal and diurnal constituents, and has an accuracy of better than ～1.5 cm for each constituent. Tidal elevations are derived from the altimeter data on the ascending and descending satellite ground tracks, and interpolated using the method of statistical interpolation. The semi‐diurnal constituents (M2, S2 and N2) compare favourably with available in‐situ observations and a numerical model. The diurnals (K1 and O1) are not as accurate as the semi‐diurnals, especially in the nearshore environment. The paper demonstrates the ability of TOPEX/POSEIDON altimetry to provide accurate tidal data over a continental shelf. 相似文献
11.
Abstract We analyse time series records of isopleth depths derived from two extended sequences of hourly and bi‐hourly sampled profiles taken at Ocean Weather Station P during the summers of 1961 and 1969. Vertical displacements to 240‐m depth are mainly of semidiurnal frequency with r.m.s. amplitudes of 1–4 m. Displacements at diurnal and near‐inertial frequencies are typically less than a metre and have little statistical significance. Within the semidiurnal band, motions appear to be predominantly at the principal solar (S2) rather than the principal lunar (M2) semidiurnal frequency. The phase of the M2 baroclinic tide is roughly equal to that of the M2 barotropic tide (as extrapolated from coastal and seamount observations); phases of other constituents differ appreciably from barotropic values. 相似文献
12.
Richard D. Ray 《大气与海洋》2016,54(2):108-116
Since the late 1990s the semi-diurnal tide at Churchill, on the western shore of Hudson Bay, has been decreasing in amplitude, with M2 amplitudes falling from approximately 154?cm in 1998 to 146?cm in 2012 and 142?cm in 2014. There has been a corresponding small increase in phase lag. Mean low water, decreasing throughout most of the twentieth century, has levelled off. Although the tidal changes could reflect merely a malfunctioning tide gauge, the fact that there are no other measurements in the region and the possibility that the tide is revealing important environmental changes calls for serious investigation. Satellite altimeter measurements of the tide in Hudson Bay are complicated by the seasonal ice cover; at most locations less than 40% of satellite passes return valid ocean heights and even those can be impacted by errors from sea ice. Because the combined TOPEX/Poseidon, Jason-1, and Jason-2 time series is more than 23 years long, it is now possible to obtain sufficient data at crossover locations near Churchill to search for tidal changes. The satellites sense no changes in M2 that are comparable to the changes seen at the Churchill gauge. The changes appear to be localized to the harbour, or to the Churchill River, or to the gauge itself. 相似文献
13.
黄海夏季潮汐锋区环流的数值研究 总被引：6，自引：0，他引：6
基于Blumberg＆Mellor三维非线性环流模型(ECOM)并结合Mellor＆Yamada的湍封闭模型，对黄海M2分潮、密度环流、锋区环流等进行了的数值模拟：潮汐模拟结果较好的体现了黄、渤海M2潮波传播系统，验证了模型的可行性；模拟密度环流的量阶和方向均与夏季实测环流保持一致，体现了密度环流是夏季总环流的重要组成部分；两个断面锋区环流的模拟结果显示锋区位置不同环流特征也不相同，锋区对应的上升流特征与锋区表面通常观测到冷水现象吻合，锋区上层水体沿潮汐锋方向流速较强。另外，数值试验结果显示了地形和潮混合对潮汐锋的形成及锋区环流有重要影响。 相似文献
14.
R.A. Flather 《大气与海洋》2013,51(1):22-45
Abstract The development of a tidal model for the west coast of Canada is described. The model is intermediate in resolution between coarse‐gridded global models and fine‐gridded local models; it provides a good representation of the main shelf regions and also includes a substantial area of the neighbouring ocean. The physical processes relevant to tides in both deep and shallow water are included. Calculations have been carried out for the M2 and K1 constituents and the model results were compared with extensive tide‐gauge observations and empirically based charts. For M2, the agreement between model results and observations is generally excellent, but for K1, which contains more small‐scale variability, the model results are not quite so good. The variability in K1 is associated with tidally generated continental shelf waves. Examination of the computed currents and energy fluxes suggests that shelf‐wave components are present in the model solution but, for the Vancouver Island shelf, their propagation is not reproduced accurately. This may be due to deficiencies in the model and/or to the influences of stratification and mean currents, which are neglected here. The model predicts that shelf‐wave components should also occur in diurnal tides on the Alaskan shelf. The significance of the tide‐generating potential and advection are also examined and further work proposed. 相似文献
15.
The forcing mechanisms for Antarctic coastal polynyas and the thermodynamic effects of existing polynyas are studied by means of an air-sea-ice interaction experiment in the Weddell Sea in October and November 1986.Coastal polynyas develop in close relationship to the ice motion and form most rapidly with offshore ice motion. Narrow polynyas occur frequently on the lee side of headlands and with strong curvature of the coastline. From the momentum balance of drifting sea ice, a forcing diagram is constructed, which relates ice motion to the surface-layer wind vector v
z
and to the geostrophic ocean current vector c
g
. In agreement with the data, wind forcing dominates when the wind speed at a height of 3 m exceeds the geostrophic current velocity by a factor of at least 33. This condition within the ocean regime of the Antarctic coastal current usually is fulfilled for wind speeds above 5 m/s at a height of 3 m.Based on a nonlinear parameter estimation technique, optimum parameters for free ice drift are calculated. Including a drift dependent geostrophic current in the ice/water drag yields a maximum of explained variance (91%) of ice velocity.The turbulent heat exchange between sea ice and polynya surfaces is derived from surface-layer wind and temperature data, from temperature changes of the air mass along its trajectory and from an application of the resistance laws for the atmospheric PBL. The turbulent heat flux averaged over all randomly distributed observations in coastal polynyas is 143 W/m2. This value is significantly different over pack ice and shelf ice surfaces, where downward fluxes prevail. The large variances of turbulent fluxes can be explained by variable wind speeds and air temperatures. The heat fluxes are also affected by cloud feedback processes and vary in time due to the formation of new ice at the polynya surface.Maximum turbulent fluxes of more than 400 W/m2 result from strong winds and low air temperatures. The heat exchange is similarly intense in a narrow zone close to the ice front, when under weak wind conditions, a local circulation develops and cold air associated with strong surface inversions over the shelf ice is heated above the open water. 相似文献
16.
Dibromomethane (CH2Br2), a natural stratospheric ozone depleting substance, is mostly emitted from the ocean, but the relative importance of coastal (or macroalgae) and open ocean emissions is unknown. We made long-term high-frequency measurements of CH2Br2 concentrations at two remote coastal sites in Japan, on the subtropical Hateruma Island (poor in macroalgae) and at Cape Ochiishi (rich in macroalgae). CH2Br2 concentrations at Hateruma showed prominent seasonal variation, being lower in summer (around 0.94 ppt) than in winter (around 1.23 ppt). In contrast, CH2Br2 concentrations at Ochiishi were highly variable, often exceeding 2 ppt in the summer but with minimum baseline concentrations close to those from Hateruma; in the winter the concentrations were almost constant at about 1.3 ppt. Analysis of the data suggested that (1) emissions from macroalgae were not likely to extend offshore, but instead were localized near the shore, (2) strong macroalgal emissions of CH2Br2 were almost limited to the summer, but it was not reflected in the seasonality of the baseline concentrations of CH2Br2 in the atmosphere, and therefore (3) macroalgal or coastal emissions of CH2Br2 in the temperate zone might have a rather limited contribution to the global CH2Br2 sources. These findings are especially important for the understanding of the tropospheric and stratospheric bromine budget. 相似文献
17.
Abstract Estimates of the rate of dissipation of turbulent energy,?v, were made on the continental shelf off the southwest coast of Vancouver Island throughout the diurnal tidal cycle at six stations. If turbulent mixing takes place away from boundaries, and a constant fraction of the energy supplied to turbulence is converted into potential energy, this dissipation rate per unit volume, ?v, is shown to be proportional to the rate of turbulent mass and nutrient flux across the isopycnals. We compute these fluxes to determine the source of nutrients in the upper mixed layer on the shelf. It is found that tidal mixing on the shelf throughout the water column contributes less than 10% of the flux of nutrients supplied by the estuarine outflow out of Juan de Fuca Strait. Strong winds during upwelling events supply nutrients at rates greater than those due to tidal mixing, but at rates that are likely smaller than the Juan de Fuca source. Therefore, the nutrient‐rich waters observed in the euphotic zone in spring and summer on this shelf derive mainly from Juan de Fuca Strait. Nutrients in bottom water derive from upwelling along shelf‐break canyons. 相似文献
18.
A long-term record of surface currents from a high-frequency radar system, along with near-surface hydrographic transects, moored current meter records, and satellite imagery, are analyzed to determine the relative importance of river discharge, wind, and tides in driving the surface flow in the Fraser River plume. The observations show a great deal of oceanographic and instrumental variability. However, averaged quantities yielded robust results. The effect of river flow, which determines buoyancy and inertia near the river mouth, was found by taking a long-term average. The resulting flow field was dominated by a jet with two asymmetric gyres; the anticyclonic gyre to the north had flow speeds consistent with geostrophy. The mean flow speed near the river mouth was 14.3?cm?s–1, while the flow further afield was 5?cm?s–1 or less. Wind stress and surface currents were highly coherent in the subtidal frequency band. Northwesterly winds drive a surface flow to the southeast at speeds of nearly 30?cm?s–1. Southeasterly winds drive a surface flow to the northwest at speeds reaching 20?cm?s–1; however, there is more spatial variability in speed and direction relative to the northwesterly wind case. A harmonic analysis was used to extract the tidally driven flows. Ellipse parameters for the major tidal constituents varied considerably in both alignment and aspect ratio over the radar domain, in direct contrast to a barotropic model which predicted rectilinear flow along the Strait of Georgia. This is a result of water filling and draining the shallow mud flats north of the Fraser's main channel. The M2 velocities at the surface were also weaker than their barotropic counterparts. However, the shallow water constituent MK3 was enhanced at the surface and nearly as strong as the mean flow, implying that non-linear interactions are important to surface dynamics. 相似文献
19.
Gilles Tedeschi Alexander M. J. van Eijk Jacques Piazzola Jolanta T. Kusmierczyk-Michulec 《Boundary-Layer Meteorology》2017,163(2):327-350
Sea-salt aerosol concentrations in the coastal zone are assessed with the numerical aerosol-transport model MACMod that applies separate aerosol source functions for open ocean and the surf zone near the sea–land transition. Numerical simulations of the aerosol concentration as a function of offshore distance from the surf zone compare favourably with experimental data obtained during a surf-zone aerosol experiment in Duck, North Carolina in autumn 2007. Based on numerical simulations, the effect of variations in aerosol production (source strength) and transport conditions (wind speed, air–sea temperature difference), we show that the surf-zone aerosols are replaced by aerosols generated over the open ocean as the airmass advects out to sea. The contribution from the surf-generated aerosol is significant during high wind speeds and high wave events, and is significant up to 30 km away from the production zone. At low wind speeds, the oceanic component dominates, except within 1–5 km of the surf zone. Similar results are obtained for onshore flow, where no further sea-salt aerosol production occurs as the airmass advects out over land. The oceanic aerosols that are well-mixed throughout the boundary layer are then more efficiently transported inland than are the surf-generated aerosols, which are confined to the first few tens of metres above the surface, and are therefore also more susceptible to the type of surface (trees or grass) that determines the deposition velocity. 相似文献
20.
利用瓦里关大气本底站甲烷观测数据对美国Aqua卫星的AIRS观测结果进行对比分析,并分析研究了2003~2012年青藏高原对流层大气甲烷的时空分布特征,结果表明:1)AIRS观测结果与近地面观测资料变化趋势一致,存在显著的正相关关系,突变时间比较一致,可以用于青藏高原区域的甲烷浓度特征分析。2)青藏高原对流层甲烷浓度在空间分布上存在显著的西北—东南走向的低值带及其南北侧存在4个固定的高值中心,分别位于阿里、那曲、山南和玉树。3)青藏高原甲烷浓度呈现显著随高度而降低的趋势,年平均甲烷浓度分别为1.810ppm(1 ppm=10-6)、1.797 ppm和1.781 ppm。在对流层中层和中上层,甲烷浓度基本呈现低值带最低、南北侧均高的山谷型分布特征。在对流层层顶,以低值带为分界线,呈现明显的南高北低特征。4)青藏高原甲烷浓度随时间呈缓慢上升趋势,平均速度为0.0018 ppm/a,夏季上升最快,秋季上升最慢。5)青藏高原甲烷存在明显的单峰型季节变化特征,夏秋季高,冬春季低,与东部地区冬、夏双峰型特征不同,随着高度上升季节变化更为明显。 相似文献