Baroclinic Tides

En la región de Magallanes Norte -entre el golfo de Penas y boca Occidental del estrecho de Magallanes-los fosfatos, nitratos, temperatura y profundidad de la capa de mezcla en la columna de agua son factores asociados a la distribución cuantitativa, diversidad biológica y productividad primaria del fitoplancton. Sin embargo, estudios recientes en zonas australes adyacentes, indican que una fuerte influencia del clima óptico de la columna de agua generan una alta heterogeneidad espacio-temporal de escala intra estacional de los patrones de distribución del fitoplancton. En canales y fiordos entre los 43 o -56 o S, se cuantificó: i). Concentración de clorofila (CL) de muestras sin fraccionar y fraccionadas por tamaños, ii). Productividad primaria (PP) diaria, iii). Diversidad específica (H') y abundancia numérica (cél L -1 ). La hipótesis es que la variabilidad en la distribución del fitoplancton está determinada por la disponibilidad de radiación fotosintéticamente activa (PAR) en la columna de agua, medida a través de los coeficientes de extinción difusa de PAR (KPAR), independientemente de la radiación estacional.

Recibido en junio de 1995; aceptado en marzo de 1996 RESUMEN Con base en un modelo lineal, se estiman los principales parámetros de las mareas y ondas internas semidiumas de altas frecuencias para la plataforma y pendiente continental cerca de las costas mexicanas de los estados de Jalisco y Colima. Por datos de la distribución vertical de la frecuencia de Brunt-Väisälä y por medio de cartas batimttricas actualizadas, se calculan las trayectorias de los flujos de energía (y) de la marea interna y la pendiente del fondo marino (a) en el talud continental, respectivamente. Se muestra que para la mayoría de las secciones del fondo se encuentran valores cercanos al crítico aly = 1, lo cual testifica que existen las condiciones favorables para la generación de las mareas internas en el area de estudio de la costa del Océano Pacífico. Con base en el modelo de Baines (1982), se realizan los cálculos del flujo de energía de la onda barotrópica M2 a las ondas internas y se estiman sus amplitudes. Se muestra que los flujos de energía y amplitud de la marea interna dependen no sólo de la intensidad de la marea barotrópica, sino también de los iingulos de su llegada al borde de la plataforma.

Vertical transport of horizontal momentum due to baroclinic instabilities is investigated in a rotating stratified fluid. The experiments were carried out in the large rotating tank of the Coriolis-LEGI laboratory in Grenoble with flat bottom and linear density stratification. The mean flow was generated by increasing (spin up) or decreasing (spin down) the rotation rate of the platform. The velocity fields were measured by PIV (Particle Image Velocimetry) technique. The dimensionless parameters that are important in determining the observed response are the Burger number and the Rossby number. Our experimental study reveals two very different behaviors. For O(1) Burger numbers, the bulk of the flow remains axisymmetric with a very slow decay. We have checked that the decay is well described by the usual vertical diffusion law, except in a region near the boundaries. The mismatch pertains to the presence of Ekman pumping/suction, but this mechanism is confined by stratification to a relatively shallow layer. For Burger numbers ≪ O(1), baroclinic instabilities are observed. The increased vertical momentum transport leads to a much faster spin than the previous case. Neither the diffusion nor the Ekman pumping/suction can be considered responsible for this enhanced transport of momentum and we interpret it as the effect of baroclinic instabilities. Eady's theory is used to analyse the quasi-geostrophic baroclinic stability problem and a model is proposed to estimate the azimuthal velocity decay. The results are presented and discussed.

We describe the concept and the experimental set-up for the laboratory experiments we carried out in the 5-m diameter rotating tank of the Norwegian University of Science and Technology in Trondheim (Norway), in June / July 2008. This set of experiments was conceived to study the barotropic instabilities that arise at the edge of the polar vortices in many planetary atmospheres. We report a few preliminary results from the analysis of the experiments.

1. un mapeado rápido al principio y al fin de la campaña para localizar el filamento y observar los cambios en el contexto general durante el estudio; Agradecimientos Quisieramos agredecer al Capitán Ramón Argibay Fernández y a la tripulación del barco por su apoyo magnífico durante la campaña. También agradecemos al equipo de la UTM sin el cuál no hubiese sido posible llevar a cabo el estudio. Damos las gracias al servicio NEODAAS del Plymouth Marine Laboratory, UK, especialmente a Dr Peter Miller, que nos proporcionó diariamente las imagenes AVHRR y Modis Aqua durante el trabajo de campo. CAIBEX es un proyecto del Plan Nacional financiado por el Ministerio de Ciencia e Innovación (CTM2007-66408).

, to investigate quantitatively the mixing processes and as a forecast tool to support emergency planning and resource management in the area. The response of the San Juan Bay circulation to both river discharges and tidal forcing has been investigated. A hind-cast simulation is performed and compared with time series measurements and hidrographic data to validate the model. Sensitivity studies to turbulence mixing parameterization have been carried out under different forcing scenarios. A simulation without river outflow but forced with tidal constituents along the open boundaries is performed. Good agreement has been found with coastal observations with amplitudes gauges and modeled amplitudes constituents. A numerical experiment of the response of the Bay's circulation to river discharge only is performed and compared with the tide plus river forcing and tidal forcing only scenarios. Salinity distributions and vertical mixing are affected by the proximity to deep waters of the San Juan Bay Estuary, also the bulge region and plume structure in the entrance of San Juan Bay are highly affected by the bottom friction for the case with tide forcing.

This study investigated the main water-level (WL) variability modes of Nokoué Lagoon in Benin (West-Africa). The average WL ranges between 1.3 and 2.3 m between the low-and high-water seasons. Seasonal as well as weak interannual variations between 2018 and 2019 are driven by rainfall regime over the catchment and associated river inflow. At sub-monthly scales, the lagoon is tidally choked: ocean tides can reach 90 cm, whereas in the lagoon semi-diurnal and diurnal tides hardly reach few centimeters. Choking conditions vary with river inflow and ocean tide amplitude, correctly represented by a simple tidal choking model. Diurnal modulation and asymmetry of the tide are stronger (weaker) during high (low) water period. We also observed WL variations of ±5-10 cm at a fortnightly frequency, stronger during wet (high-water) season. Superimposed on the seasonal, fortnightly and tidal WL variations, we further observed short-term high-frequency seiche events. Mostly observed during dry (low-water) conditions, they are characterized by typical standing-wave oscillations of 5-10 cm amplitudes and 3 h periods. They are forced by the passage of fast-moving squall-lines that induce strong wind variations, heavy rainfalls and rapid drop-off of the air temperature. Results obtained in this study provide useful metrics for the validation of flood forecasting models to be implemented in Benin, and elsewhere on the West African coastline.

Using the 13 m diameter LEGI-Coriolis rotating platform, the evolution processes of a generated anticyclonic eddy throughout its lifecycle are analyzed. Experimental results have shown that the eddy lasted for approximately 3T0, where T0 is the rotating period of 90 s. After T = 0.3T0, the eddy enters its mature phase, whereby following this event, eddy intensity slowly decreases from its maximum rotation speed. By T = 2.6T0, the eddy enters a stage of rapid weakening. In its decay period, two underlying mechanisms for this decay have been identified as inertial instability and eddy–eddy interactions.

In the sub-mesoscale ocean vortices tend to be predominantly cyclonic [4]. Inertial instability (hereafter II), which is a centrifugal instability mechanism in the presence of the Coriolis force, is a destructive mechanism that acts only on anti-cyclones, and therefore is hypothesized to cause this asymmetry. Furthermore, since II is in fact the growth of the overturning vorticity, thus creating vertical mixing, it is expected to contribute to nutrient enrichment from the deep, affecting primary production and the oceanic carbon cycle. Linear stability analysis [6] shows that three-dimensional unstable modes of parallel shear flow (without curvature) may have stronger growth rates than the standard two-dimensional barotropic modes when the absolute vorticity is negative, thus II is more significant than shear instability in the destruction of strong anticyclonic shear. For circular vortices (with curvature), vortex columns are unstable to 3D perturbations where the generalized Rayle...

The stability of axisymmetric oceanic-like vortices to inertial perturbations is investigated by means of linear stability analysis, taking into account the thickness and the stratification of the thermocline, as well as the vertical eddy viscosity. The model considers different types of circular barotropic vortices in a linearly stratified shallow layer confined with rigid lids. In this case the aspect ratio (thermocline height to vortex radius ratio) should be added to the parameters that control the stability for columnar vortices, which are the stratification, and the Ekman and Rossby numbers. We show that for strong stratification the Burger number (the radius of the vortex in relation to the Rossby radius of deformation) replaces the aspect ratio and the stratification parameter, and then only three parameters are needed. Numerical analysis reveals that if the intensity of the vortex is characterized by the vortex Rossby number, then for monotonic and non-isolated vortices, the instability is not sensitive to the vorticity profile. This allows extending our analytical solutions for the Rankine vortex to a wide variety of oceanic cases, including results such as the analytic dispersion relation, and the marginal stability criterion. This criterion suits oceanic conditions better than the generalized Rayleigh criterion, which is only valid for non-dissipative and non-stratified eddies. Comparison with literature oceanographic data shows that our criterion allows for cases that seem to contradict the common oceanographic hypothesis for inertial instability: 1. Intense submesoscale anticyclones may be stable even with a core region of negative absolute vorticity; and on the other hand, 2. mesoscale vortices can be unstable. We corroborate our findings with large-scale laboratory experiments, performed at the LEGI-Coriolis platform.

Several aspects of the vortex asymmetry leeward of islands were studied with laboratory experiments conducted at the LEGI-Coriolis in Grenoble (France). A total of sixty-seven experiments were conducted and the impact of rotation and stratification on small-scale inertial instabilities was considered. The experimental setup mimics the upper thermocline layer on the top of a deep barotropic ocean. Symmetric, asymmetric and multiple islands arrangements were considered during the experiments. Preliminary results suggest that small-scale inertial instability could affect the dynamics of anticyclonic vortices in the far-field wake but also in the near-field wake one or two diameter behind the island. The stabilizing impact of the stratification may lead to stable anticyclones even for finite relative vorticity (ξ/f<-1). Moreover, asymmetrical island or archipelago geometry may also induce significant asymmetries in the wake.

Fluorometric measurements were taken from a CTD at San Jorge Bay (northern Chile) to adjust a Gaussian model, in order to determine the vertical distribution of phytoplankton biomass using satellite-derived chlorophyll a data. Calibration was done using two in situ data sets. Each chlorophyll a profile was smoothed by a moving average and adjusted with a Gaussian model, obtaining the mean Gaussian parameters for both data sets. The mean Gaussian model obtained for one of the data sets was valid for a chlorophyll a range between 1.17 and 51.8 mg m-3 , and the maximum concentration was located at 19.20 and 0.25 m depth, respectively. The 20 January 2011 color image was analyzed for the study area, and the modal concentration was 0.78 mg m-3 , with 95% of the data varying between 0.5 and 20.0 mg m-3. The adjusted mean Gaussian model was valid for 80.26% of the study area. The analysis was expanded to the rest of January 2011 (14 images), and the model was valid for 84.40% (±12.48%) of the study area. The same procedure was followed but without applying the moving average to the in situ data, and the Gaussian model obtained in this case was valid for 93.72% (±8.89%) of the study area. Other studies of the optical properties of water are required for a better interpretation of the color images for this coastal system.

Fluorometric measurements were taken from a CTD at San Jorge Bay (northern Chile) to adjust a Gaussian model, in order to determine the vertical distribution of phytoplankton biomass using satellite-derived chlorophyll a data. Calibration was done using two in situ data sets. Each chlorophyll a profile was smoothed by a moving average and adjusted with a Gaussian model, obtaining the mean Gaussian parameters for both data sets. The mean Gaussian model obtained for one of the data sets was valid for a chlorophyll a range between 1.17 and 51.8 mg m–3, and the maximum concentration was located at 19.20 and 0.25 m depth, respectively. The 20 January 2011 color image was analyzed for the study area, and the modal concentration was 0.78 mg m–3, with 95% of the data varying between 0.5 and 20.0 mg m–3. The adjusted mean Gaussian model was valid for 80.26% of the study area. The analysis was expanded to the rest of January 2011 (14 images), and the model was valid for 84.40% (±12.48%) of th...

, to investigate quantitatively the mixing processes and as a forecast tool to support emergency planning and resource management in the area. The response of the San Juan Bay circulation to both river discharges and tidal forcing has been investigated. A hind-cast simulation is performed and compared with time series measurements and hidrographic data to validate the model. Sensitivity studies to turbulence mixing parameterization have been carried out under different forcing scenarios. A simulation without river outflow but forced with tidal constituents along the open boundaries is performed. Good agreement has been found with coastal observations with amplitudes gauges and modeled amplitudes constituents. A numerical experiment of the response of the Bay's circulation to river discharge only is performed and compared with the tide plus river forcing and tidal forcing only scenarios. Salinity distributions and vertical mixing are affected by the proximity to deep waters of the San Juan Bay Estuary, also the bulge region and plume structure in the entrance of San Juan Bay are highly affected by the bottom friction for the case with tide forcing.

A vortex placed at an initially straight density interface winds it into an ever-tightening spiral. This flow then displays rich dynamics, due to inertial effects caused by density stratification (non-Boussinesq effects), and gravitational effects. In the absence of gravity we showed recently that the flow is subject to centrifugal Rayleigh-Taylor and spiral Kelvin-Helmholtz instabilities. The latter grows slightly faster than exponentially. In this paper we present computations including gravity with and without and with inertial effects. Gravity modifies the spiralling process and contributes to the breakdown of the vortex. When both effects are allowed to operate together, the resulting flow has a complex radial character, with small-scale structures near the vortex core attributed to non-Boussinesq effects, and large scale roll-up due to gravity followed by breakdown.

Field data collected during June 2005 were used to determine the relationship between the second fluorescence maximum (FMax), the top of the oxygen minimum zone (OMZ), and physical processes (coastal currents, eddies, and upwelling) in the northern region of the Eastern Tropical Pacific off Mexico (ETPM). A recurrent second FMax was observed in the ETPM, which was formed only when the upper limit of the OMZ (9.0 µmol L–1) overlapped with the 1% downwelling blue irradiance depth (Ed490). The presence of the second FMax increased the total integrated water column chlorophyll from 20% to 40%. The second FMax was absent from areas where oxygenated California Current Water (CCW) deepened the upper limit of the OMZ below 1% Ed490. The poleward Mexican Coastal Current carried less oxygenated Subtropical Subsurface Water into the area, and enabled the formation of the second FMax. The variability of the second FMax driven by mesoscale physical processes was related to coastal upwelling and ...

In this work, 16 stations in Cienfuegos Bay were optically classified in the period from 2009 to 2014 and the spatio-temporal variation of the average attenuation coefficient of light was determined, as well as its relationship with chlorophyll a and suspended solids. The average attenuation coefficient was estimated from an empirical relationship ReVIsTA INVesTIGACIONes MARINAs

Between 1989 and 1991 the authors made observations that confirm and elucidate the coupling between harbor seiches at Puerto Princesa on Palawan Island in the Philippines and tide-generated internal solitons in the Sulu Sea. Published tidal current predictions for Basilan Strait in the Sulu Archipeligo were used to produce an index to the daily ebb tidal flows nea•r Pearl Bank where the solitons originate. The coherence between predicted maximum ebb tidal current speed and observed seiche activity was 0.60 and the phase lag between the two quantities closely matched published estimates of the time required for solitons to cross the Sulu Sea. Arrival of the Sulu Sea waves immediately offshore of Puerto Princesa in the form of internal bores corresponded in time to the initiation of harbor seiche activity. A more precise estimate of soliton travel time was determined from the time difference between predicted maximum ebb current and the initiation •of seiche activity, and it was found to have a remarkably regular seasonal pattern, which can be largely explained by seasonal variations in Sulu Sea temperature and salinity stratification. Therefore, the timing of seiche events at Puerto Princesa can be forecast based on Sulu Archipeligo tide predictions and soliton travel time. In general, the fortnightly pattern of seiche magnitude follows that of tidal current predictions, but day-today deviations are common. Seiche magnitude varies seasonally with generally low activity during the winter (northeast) monsoon and usually maximum activity late in the summer (southwest) monsoon. VOLUME 28 * Woods Hole Oceanographic Institution Contribution Number 9343.

Vertical temperature profiles were measured near the shelf edge off the coast of Palawan Island (Philippines) during the passage of several "rip bands" of choppy surface waves. Such rip bands are commonly associated with internal waves. Coincident with the passage of one of the rip bands, the temperature near the bottom decreased by 2.5°C within 1.4 min, becoming colder than any water on the shelf. Furthermore, the apparent depth of our CTD decreased by about 8 m despite the fact that the "line-out" was held fixed. We interpret these limited data, along with a sea-level record, as evidence of internal swash created by breaking internal solitary waves which are generated by tidal flow over a shallow bank in the southeastern Sulu Sea (described by

A numerical model in slice configuration was applied to the Central Andaman Sea in order to derive metocean operational and design criteria associated to internal solitary waves which are large amplitude interfacial waves. For that purpose, a 10 year hindcast was generated. The model was driven by tides at the open boundary and included realistic stratification and topography. The results have been compared to data mostly taken from satellites and proved to be accurate in determining parameters such as phase speed and interpacket distance. The phase speeds range from 2.21 m/s in March to 2.5 m/s in November. Corresponding interpacket distances range from 99 km to 111 km in close agreement with available data. According to the model results internal solitary waves are more/less frequent in March/August. Model outputs were specifically analyzed at 2 arbitrary locations. Maximum current speeds obtained with the model at those locations occur in November reaching a value close to 1.5 m/...

We study the formation of lenses of the ocean's intermediate water using a 2.5-layer {3plane primitive equation model with localized injection of water mass. For the injecting rate of 1.0 Sv, we have observed that strong vortices are shed regularly. These vortices propagate westward much faster than the second baroclinic long Rossby wave. They are totally isolated from each other and show strong baroc1inicity as well. Moreover, they remain stable over a sufficiently long period of time. Regular formation of such strong vortices in the intermediate layer has not been reported previously. The translation speed is explained using the Euler's momentum integral theorem for the nonlinear baroc1inic vortex on the {3-plane. We have demonstrated that coupling between the primary motion in the intermediate layer and the secondary motion in the upper layer with a meridion al shift is crucial to the fast westward translation of the intense vortices. A simple dispersion formula relating the zonal translation speed with the vortex radius is also derived under the assumption of quasi-geostrophy. It has turned out that the analytic al relation explains the numerical results surprisingly well despite the limitation of its derivation.

Several aspects of the vortex asymmetry leeward of islands were studied with laboratory experiments conducted at the LEGI-Coriolis in Grenoble (France). A total of sixty-seven experiments were conducted and the impact of rotation and stratification on small-scale inertial instabilities was considered. The experimental setup mimics the upper thermocline layer on the top of a deep barotropic ocean. Symmetric, asymmetric and multiple islands arrangements were considered during the experiments. Preliminary results suggest that small-scale inertial instability could affect the dynamics of anticyclonic vortices in the far-field wake but also in the near-field wake one or two diameter behind the island. The stabilizing impact of the stratification may lead to stable anticyclones even for finite relative vorticity (ξ/f&lt;-1). Moreover, asymmetrical island or archipelago geometry may also induce significant asymmetries in the wake. 1.

Several aspects of the vortex asymmetry leeward of islands were studied with laboratory experiments conducted at the LEGI-Coriolis in Grenoble (France). A total of sixty-seven experiments were conducted and the impact of rotation and stratification on small-scale inertial instabilities was considered. The experimental setup mimics the upper thermocline layer on the top of a deep barotropic ocean. Symmetric, asymmetric and multiple islands arrangements were considered during the experiments. Preliminary results suggest that small-scale inertial instability could affect the dynamics of anticyclonic vortices in the far-field wake but also in the near-field wake one or two diameter behind the island. The stabilizing impact of the stratification may lead to stable anticyclones even for finite relative vorticity (ξ/f<-1). Moreover, asymmetrical island or archipelago geometry may also induce significant asymmetries in the wake.

Here we extend the Madelung transformation of the Schrödinger equation into a fluidlike form to include the influence of an external electromagnetic field on a charged particle. The vorticity of the Madelung fluid is then in the opposite direction to the imposed magnetic field and equal in magnitude to the cyclotron angular frequency. When the particle motion is confined to a plane, perpendicular to an imposed magnetic field, the equivalent flow dynamics is that of zero absolute vorticity obtained in a quasi 2D rotating frame, where the cyclotron frequency plays a role equivalent to that of the Coriolis frequency in a rotating frame. We show how the Landau levels and the extended modes in the integer quantum Hall effect are all mapped into such zero absolute vorticity-like plane Couette flows, where the latter exhibit a geostrophic-like balance between the magnetic force and the gradients of the quantum (Bohm) potential and the electric force.

This paper investigates the three-dimensional stability of a pair of co-rotating vertical vortices in a rotating strongly stratified fluid. In a companion paper (Otheguy, Chomaz & Billant 2006), we have shown that such a basic flow in a strongly stratified fluid is affected by a zigzag instability which bends the two vortices symmetrically. In the non-rotating flow, the most unstable wavelength of this instability scales as the buoyancy length and its growth rate scales as the external strain that each vortex induces on the other one. Here, we show that the zigzag instability remains active whatever the magnitude of the planetary rotation and is therefore connected to the tallcolumn instability in quasi-geostrophic fluids. Its growth rate is almost independent of the Rossby number. The most amplified wavelength follows the universal scaling λ =2πF h b γ 1 /Ro 2 + γ 2 /Ro + γ 3 ,w h e r eb is the separation distance between the two vortices, (γ 1 , γ 2 , γ 3) are constants, F h is the horizontal Froude number and Ro the Rossby number (F h = Γ/πa 2 N, Ro = Γ/πa 2 f ,whereΓ is the circulation of each vortex, a the vortex radius, N the Brunt-Väisälä frequency and f the Coriolis parameter). When Ro = ∞, the scaling λ ∝ F h b found in the companion paper Otheguy et al. (2006) is recovered. When Ro → 0, λ ∝ bf /N in agreement with the quasi-geostrophic theory. In contrast to previous results, the wavelength is found to depend on the separation distance between the two vortices b, and not on the vortex radius a.

Models of the Great Red Spot authors' conclude the GRS must be IG. Voyager data , however, show that the GRS velocity is mostly in a thin , large diam eter, annular region. The correct length scale to compare with r, is the halfwidth of this annulus, approximately 2,000 km , which is the characteristic scale l over which the velocity varies. A careful comparison of Voyager data with numerical solutions of full shallow-water equations yields'' "' 2,000 km ~ r,~ 3,000 km ; hence , the QG approximation for the GRS is justified. The numerical solutions also show that the potential vorticity q can be approximated to within 15% by the QG expression q=Q[(J+wt 1 'V.lf 1 'Vgh)gh(Jr,f' ], where w and Q are the vorticity and potential vorticity of the zonal velocity, h the height of the upper surface of the vortex not including the zonal com

The northeast South China Sea is perhaps the largest internal tide energy source in the world. The temporal variability of internal tides was investigated on the basis of 8-month moored acoustic Doppler current profiler observations on the continental slope at the Dongsha Plateau. The daily amplitude and phase of diurnal and semidiurnal internal tides were determined from complex demodulation, and the dominant spatial and temporal patterns were extracted with empirical orthogonal function (EOF) analysis. The EOF modal structures showed good agreement with the normal mode solution, although vertical phase propagations were apparent. The first semidiurnal EOF mode corresponded to the first normal mode, and the first two diurnal EOF modes corresponded to the second and third normal modes, respectively. The modal structure and energy flux also were consistent with previous observations near the shelf break from the Asian Seas International Acoustic Experiment. On the other hand, the amplitudes of diurnal and semidiurnal EOF modes both indicated large irregular fortnightly variations that were not phase locked (incoherent) with astronomical forcing. The study highlighted the importance of incoherent internal tidal motion, which accounted for about three fourths of the observed tidal energy.

We present a numerical model that reveals a mechanism governing the polar atmospheric dynamics of Jupiter, Saturn, Uranus and Neptune. Exploration of the polar regions of the gas giants has produced surprisingly diverse results, with Cassini finding a single, intense, compact polar cyclone precisely centered on each pole of Saturn, and Voyager data and ground-based observations suggesting Uranus and Neptune have dominant, single polar cyclones as well. The Juno spacecraft at Jupiter finds several tightly packed cyclones surrounding a central cyclone offset from the poles. These discoveries raise questions about the mechanism that differentiates these polar atmospheric dynamics regimes. To help determine what physical mechanisms control these differences, we use the Explicit Planetary Isentropic Coordinate (EPIC) model to carry out forced-turbulence shallow-water simulations in a gamma-plane configuration, i.e. a Cartesian grid with a pole placed at the center. The model is forced by small-scale stochastic mass pulses that parametrically represent cumulus storms. The effects of three parameters, the planetary Burger number, Bu = (L d / a) 2 (L d is the Rossby deformation radius, a is the planetary radius), input storm strength, s, and proportion of cyclonic and anticyclonic storms injected into the domain, α, are systematically investigated. Bu emerges to be the most important, able to distinguish between four distinct dynamical regimes, matching those of the giant planets, which from large to small Bu, are: i) a large cyclonic polar vortex (i.e., Uranus/Neptune-like), ii) a compact intense cyclonic polar vortex (Saturn-like), iii) two large vortices or one vortex offset from the pole (transitional), and iv) meandering jets with no centrally dominant vortex, or with multiple circumpolar cyclones (Jupiter-like). The boundaries of these regimes are found to be only slightly modulated by the values of s and α. By applying this correlation with respect to Bu in reverse, an observation of a particular polar regime could in principle be used to constrain L d .

This paper investigates the dynamics of the deep chlorophyll maximu m layer (DCM L) along the Fernando de Noronha Ridge in the oligotrophic western equatorial Atlantic off northeast Brazil. M ixing processes between water masses above and below the thermocline may occur in a scale of tens of meters around the 24.5 to 25.5 isopycnals, where photoautotrophs are concentrate at the bottom of the euphotic zone. The primary production at the DCM L can provide 210 (±170) metric tons of Carbon per day to the benthic community at the Rocas atoll. The behavior of isopycnals in deeper and strongly stratified waters suggest that internal waves may imp rove primary production, by lift ing the deeper and nutrient-rich South Atlantic Central Water upwards and carrying the autotrophs to brighter depths.

The Juno mission to Jupiter has found closely packed cyclones at the planet’s two poles. The observation that these cyclones coexist in very confined space, with outer rims almost touching each other but without merging, poses a big puzzle. In this work, we present numerical calculations showing that convectively sustained, closely packed cyclones can form and survive without merging for a very long time in the polar region of a deep rotating convection zone (for thousands of planetary rotation periods). Through an idealized application of the inertial stability criterion for axisymmetric circulations, it is found that the large Coriolis parameter near the pole plays a crucial role in allowing the cyclones to be packed closely.

Con base en un modelo lineal, se estiman los principales parámetros de las mareas y ondas internas semidiumas de altas frecuencias para la plataforma y pendiente continental cerca de las costas mexicanas de los estados de Jalisco y Colima. Por datos de la distribución vertical de la frecuencia de Brunt-Väisälä y por medio de cartas batimttricas actualizadas, se calculan las trayectorias de los flujos de energía (y) de la marea interna y la pendiente del fondo marino (a) en el talud continental, respectivamente. Se muestra que para la mayoría de las secciones del fondo se encuentran valores cercanos al crítico aly = 1, lo cual testifica que existen las condiciones favorables para la generación de las mareas internas en el area de estudio de la costa del Océano Pacífico. Con base en el modelo de Baines (1982), se realizan los cálculos del flujo de energía de la onda barotrópica M2 a las ondas internas y se estiman sus amplitudes. Se muestra que los flujos de energía y amplitud de la marea interna dependen no sólo de la intensidad de la marea barotrópica, sino también de los iingulos de su llegada al borde de la plataforma.

En la región de Magallanes Norte-entre el golfo de Penas y boca Occidental del estrecho de Magallanes-los fosfatos, nitratos, temperatura y profundidad de la capa de mezcla en Palabras claves: Productividad primaria diaria, concentración de clorofila, abundancia del fitoplancton, radiación fotositéticamente activa, zona eufótica, coeficiente de atenuación difusa.

The stability of axisymmetric oceanic-like vortices to inertial perturbations is investigated by means of linear stability analysis, taking into account the thickness and the stratification of the thermocline, as well as the vertical eddy viscosity. The model considers different types of circular barotropic vortices in a linearly stratified shallow layer confined with rigid lids. In this case the aspect ratio (thermocline height to vortex radius ratio) should be added to the parameters that control the stability for columnar vortices, which are the stratification, and the Ekman and Rossby numbers. We show that for strong stratification the Burger number (the radius of the vortex in relation to the Rossby radius of deformation) replaces the aspect ratio and the stratification parameter, and then only three parameters are needed. Numerical analysis reveals that if the intensity of the vortex is characterized by the vortex Rossby number, then for monotonic and non-isolated vortices, the instability is not sensitive to the vorticity profile. This allows extending our analytical solutions for the Rankine vortex to a wide variety of oceanic cases, including results such as the analytic dispersion relation, and the marginal stability criterion. This criterion suits oceanic conditions better than the generalized Rayleigh criterion, which is only valid for non-dissipative and non-stratified eddies. Comparison with literature oceanographic data shows that our criterion allows for cases that seem to contradict the common oceanographic hypothesis for inertial instability: 1. Intense submesoscale anticyclones may be stable even with a core region of negative absolute vorticity; and on the other hand, 2. mesoscale vortices can be unstable. We corroborate our findings with large-scale laboratory experiments, performed at the LEGI-Coriolis platform.

Our long-term goal is to characterize and understand the physical oceanographic and atmospheric processes that determine the structure, circulation and variability of the northeastern Caribbean Sea and of the adjacent western tropical Atlantic. SCIENTIFIC OBJECTIVES The main scientific objective in this project is to accurately measure the exchange of North Atlantic and Caribbean Sea waters through Mona Passage and to determine the mean transport and flow variability at time scales from hourly to interannual.

This paper presents a comparative study on the investigation of coherent modes in chaotic time series data based on two techniques: the empirical mode decomposition and the discrete wavelet transform. We have applied these techniques to the different types of chaotic time series data obtained from a glow discharge plasma. The discrete wavelet transform and empirical mode decomposition analysis of the chaotic time series, combined with some simple statistical estimations like variance and correlation coefficient, helps in identifying the presence of coherent modes. We carried out a bicoherency analysis on the coherent modes extracted using empirical mode decomposition to detect the interactions amongst them. It is quite likely that the interactions between the different plasma modes are responsible for such turbulent nonlinear oscillations.

The Maluku Channel is a major opening of the eastern Indonesian Seas to the western Pacific Ocean, the upper-ocean currents of which have rarely been observed historically. During December 2012–November 2016, long time series of the upper Maluku Channel transport are measured successfully for the first time using subsurface oceanic moorings. The measurements show significant intraseasonal-to-interannual variability of over 14 Sv (1 Sv ≡ 106 m3 s−1) in the upper 300 m or so, with a mean transport of 1.04–1.31 Sv northward and a significant southward interannual change of over 3.5 Sv in the spring of 2014. Coincident with the interannual transport change is the Mindanao Current, choked at the entrance of the Indonesian Seas, which is significantly different from its climatological retroflection in fall–winter. A high-resolution numerical simulation suggests that the variations of the Maluku Channel currents are associated with the shifting of the Mindanao Current retroflection. It is ...

El afloramiento en la costa oeste de la Peninsula Iberica es de gran importancia en la riqueza pesquera de las costas de Galicia y por lo tanto, en la estructura socioeconomica de la region. Este fenomeno es detectable mediante satelites que miden la temperatura superficial del mar (sensor AVHRR del NOAA) y la concentracion de clorofila (sensor SeaWiFS). Actualmente el Laboratorio de Sistemas de la Universidad de Santiago de Compostela dispone de la infraestructura necesaria para el envio de imagenes termicas a la flota pesquera; pero dado el caracter restrictivo de las imagenes de clorofila, estas no se pueden enviar en tiempo real. Esto sugiere el utilizar las imagenes de temperatura para generar a partir de ellas imagenes de concentracion de clorofila, idea que surge del analisis visual de pares de imagenes de temperatura y clorofila en donde se advierte que existe una correlacion entre ellas. En este estudio se presentan las herramientas y aplicaciones informaticas desarrolladas...

Se discuten los resultados de un experimento especial de medición de parámetros espaciotemporales de las ondas internas en la ancha plataforma continental de la parte noroeste de la Bahía de Banderas. Las mediciones oceanográficas consistieron en: (a) un levantamiento rápido con un CTD ondulante a lo largo de un transecto perpendicular a la costa, (b) el remolque de una cadena de sensores de temperatura y profundidad repetidas veces sobre la plataforma continental por transectos perpendiculares a la costa y (c) series de tiempo de componentes de velocidad registradas con un perfilador de corrientes acústico Doppler colocado en el fondo de la bahía, a una profundidad de 28 m. Se determinó la presencia de ondas internas generadas por la marea semidiurna, con características correspondientes al segundo modo normal de oscilación de acuerdo con la teoría lineal de ondas internas. El análisis de los datos obtenidos mostró que, en el área de estudio, las ondas internas generadas en el talu...

 Nonlinear dynamics of 3D centrifugal instability are revealed for thin pancake vortices.  Mechanisms of enhanced energy decay due to toroidal circulation cells are described.  In cyclones, the Earth's rotation limits the energy decay related to centrifugal instability

Algorithms are presented using remote sensing optical depth, 1/K490, to estimate the depth of the euphotic zone and depths where spectral irradiance at 490 nm are 10%, 3%, 1% and 0.3% of incident surface value. The linear empirical models are derived using data from radiometric profiles measured at various locations in the Gulf of California during cruises in 1995, 1997 and 1998. The models apply to three geographically and temporally separate bio-optical provinces of the gulf: the northern basin, the Midriff Islands and the southern basins. Relative uncertainties of the regression models for the 1% light depths for both spectral irradiance (490 nm) and EPAR range from approximately 5% in the northern basin to 10% in the southern basins.

 During the late-fall, an experiment was performed in the midriff island region of the Gulf of California to study the internal wave effect on primary production and phytoplankton biomass temporal variability. A spot east of the Ángel de la Guarda Island was monitored during 48 hours, and water samples were taken for measuring pH, dissolved oxygen, inorganic nutrients (NO3 and PO4) and chlorophyll a. Photosynthesis-irradiance curves were generated for phytoplankton collected from depths corresponding to 50% and 1% light levels. With spring tides, internal waves altered significantly the water column structure, with a change in the stratification field. Nutrient concentrations at depths &gt; 20 m increased by as much as two-fold, with addition of &gt; 1.0 µM for PO4 and &gt; 7.0 µM for NO3. Chlorophyll a increased by more than 40%, between the surface and the deep chlorophyll maximum, during the same period. The assimilation number, P*m, for the 50%Eo depth decreased to near 20% of i...

Vertical and seasonal distribution of the biogeochemical tracer N* was estimated to delineate the key pathways that regulate nitrogen in the Alfonso Basin, Bay of La Paz, between February 2012 - March 2013. We used data of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) concentrations from four levels in the euphotic zone (100, 33, 3, and 0.1% I0) and another four depths below it (150, 200, 250 and 300 m). For the calculation of N*, its constants were reestimated from the original equation based on historical data of nutrients compiled between December 2005 - December 2012. Detection of anomalies on the mean ratio of NID:DIP (13.16) indicated a predominance of negative values corresponding to a greater removal of NID, especially below the 150 m, under hypoxic conditions (&lt; 1.4 ml l-1) and during periods of high biological production for the area. The incidence of these values could be associated to the local denitrification process, as well as advection of water masses fr...

The Hilbert-Huang Transform (HHT) is extended to the time series analysis of wave orbital velocities resulting fr om the superposition of waves propagating in different directions. On a theoretical basis, it is shown that an apparently chaotic velocity signal may result from the interaction of three or more waves, each one with its own period and direction of propagation. Such result is compatible with records of PUV instruments. The comparison between bivariate HHT with Fourier directional analysis shows several advantages of the former, such as identification of wave groups and non-linear interaction components.

The Hilbert-Huang Transform (HHT) is extended to the time series analysis of wave orbital velocities resulting from the superposition of waves propagating in different directions. On a theoretical basis, it is shown that an apparently chaotic velocity signal may result from the interaction of three or more waves, each one with its own period and direction of propagation. Such result is compatible with records of PUV instruments. The comparison between bivariate HHT with Fourier directional analysis shows several advantages of the former, such as identification of wave groups and non-linear interaction components.

One prominent feature in the atmospheres of Jupiter and Saturn is the appearance of large-scale vortices. However, the sustaining mechanism of these large-scale vortices remains unclear. One possible mechanism is that these large-scale vortices are driven by rotating convection. Here we present numerical simulation results on rapidly rotating Rayleigh-Bénard convection at a small Prandtl number P r = 0.1 (close to the turbulent Prandtl numbers of Jupiter and Saturn). We have identified four flow regimes in our simulation: multiple small vortices, coexisted large-scale cyclone and anticyclone, large-scale cyclone, and turbulence. The formation of large-scale vortices requires two conditions to be satisfied: the vertical Reynolds number is large (Re z ≥ 400), and the Rossby number is small (Ro ≤ 0.4). Large-scale cyclone first appears when Ro decreases to be smaller than 0.4. When Ro further decreases to be smaller than 0.1, coexisted large-scale anticyclone emerges. We have studied the heat transfer in rapidly rotating convection. The result reveals that the heat transfer is more efficient in the anticyclonic region than in the cyclonic region. Besides, we find that 2D effect increases and 3D effect decreases in transporting convective flux as rotation rate increases. We find that aspect ratio has an effect on the critical Rossby number for the emergence of large-scale vortices. Our results provide helpful insights on understanding the dynamics of large-scale vortices in gas giants.

Rapid and accurate detection of measles virus is important for case diagnosis and public health management. This study compared the performance of two monoplex RT-PCR reactions targeting the H and N genes to a duplex RT-PCR targeting both genes simultaneously. The duplex simplified processing without compromising assay performance characteristic.