scholarly journals Three-Dimensional Evolution of Large-Amplitude Internal Waves in the Strait of Gibraltar

2009 ◽  
Vol 39 (9) ◽  
pp. 2230-2246 ◽  
Author(s):  
Vasiliy Vlasenko ◽  
Jose C. Sanchez Garrido ◽  
Nataliya Stashchuk ◽  
Jesus Garcia Lafuente ◽  
Miguel Losada
Keyword(s):  
Internal Waves ◽  
Large Amplitude ◽  
Wave Train ◽  
Three Dimensional ◽  
Regular Structure ◽  
Strait Of Gibraltar ◽  
Multiple Reflections ◽  
In Situ Data ◽  
Scattered Energy

Abstract The modeling of large-amplitude internal waves (LAIWs) propagating in the Strait of Gibraltar is carried out using a fully nonlinear nonhydrostatic numerical model. The focus of the modeling efforts was on three-dimensional peculiarities of LAIW evolution, namely, cross-strait variability, interaction with lateral boundaries (including wave breaking and water mixing), radiation of secondary waves from orographic features, and interaction of secondary scattered internal waves. The along-channel propagation of packets of LAIWs reveals remarkable three-dimensional behavior. Due to the Coriolis force and multiple reflections from the lateral boundaries, the largest leading LAIW loses its energy much faster than that in the packet tail, which captures the scattered energy from the leading wave as it propagates and grows in amplitude. As a result of the energy transfer, the initially rank-ordered wave packet loses its regular structure to evolve into a non-rank-ordered wave train. In situ data collected in the eastern part of the Strait of Gibraltar confirm the idea that the non-rank-ordered structure is a common feature of internal wave packets emerging from the strait into the Alboran Sea.

scholarly journals Active Surface with Dynamic Microstructures and Hierarchical Gradient Enabled by in situ Pneumatic Control

Micromachines ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 992
Author(s):  
Jian-Nan Wang ◽  
Benfeng Bai ◽  
Qi-Dai Chen ◽  
Hong-Bo Sun
Keyword(s):  
Large Amplitude ◽  
Three Dimensional ◽  
Active Surface ◽  
Bonding Process ◽  
Dynamic Topography ◽  
Large Area ◽  
Pneumatic Control ◽  
Design Flexibility ◽  
Surface Microstructures

An active surface with an on-demand tunable topography holds great potential for various applications, such as reconfigurable metasurfaces, adaptive microlenses, soft robots and four-dimensional (4D) printing. Despite extensive progress, to achieve refined control of microscale surface structures with large-amplitude deformation remains a challenge. Moreover, driven by the demand of constructing a large area of microstructures with increased complexity—for instance, biomimetic functional textures bearing a three-dimensional (3D) gradient—novel strategies are highly desired. Here, we develop an active surface with a dynamic topography and three-tier height gradient via a strain-tunable mismatching-bonding process. Pneumatic actuation allows for rapid, reversible and uniform regulation of surface microstructures at the centimeter scale. The in-situ modulation facilitates large-amplitude deformation with a maximum tuning range of 185 μm. Moreover, the structural gradient can be modulated by programming the strain value of the bonding process. With our strategy, another two types of surfaces with a four-tier gradient and without gradient were also prepared. By providing active modulation and design flexibility of complicated microstructures, the proposed strategy would unlock more opportunities for a wealth of novel utilizations.

Modeling of channel processes in large rivers with the use of field data

2021 ◽  
Vol 9 (1) ◽  
pp. 87-102
Author(s):  
A.T. Zinoviev ◽  
◽  
A.V. Dyachenko ◽  
K.B. Koshelev ◽  
K.V. Marusin ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Anthropogenic Impacts ◽  
Three Dimensional ◽  
Large Rivers ◽  
Observation Data ◽  
Channel Processes ◽  
Channel Deformations ◽  
Study Section ◽  
In Situ Data

The paper deals with mathematical description of channel processes occurring in long sections of large rivers with a complex morphometry. To forecast negative manifestations of channel deformations, a computer model of river sediment transport in the study section is proposed. It is based on a three-dimensional (3D) / two-dimensional horizontal (2DH) flow model, a 2DH model of bed sediment transport and observation data. Comparative analysis of simulation results of channel processes in the Ob river section at the Barnaul water intakes and in situ data makes it possible to evaluate forecast capabilities of the designed model, in particular, for quantitative assessment of changes in channel topography of the study section caused by natural and anthropogenic impacts.

The MLT distribution and detailed structure of ring current:  MMS observations

2021 ◽  
Author(s):  
Xin Tan ◽  
Malcolm Dunlop ◽  
Xiangcheng Dong ◽  
Yanyan Yang ◽  
Christopher Russell
Keyword(s):  
Current Density ◽  
Large Scale ◽  
Ring Current ◽  
Current System ◽  
Radial Profile ◽  
Three Dimensional ◽  
Current Density Distribution ◽  
Magnetic Storms ◽  
In Situ Data

<p>The ring current is an important part of the large-scale magnetosphere-ionosphere current system; mainly concentrated in the equatorial plane, between 2-7 R<sub>E</sub>, and strongly ordered between ± 30 ° latitude. The morphology of ring current directly affects the geomagnetic field at low to middle latitudes. Rapid changes in ring current densities can occur during magnetic storms/sub-storms. Traditionally, the Dst index is used to characterize the intensity of magnetic storms and to reflect the variation of ring current intensity, but this index does not reflect the MLT distribution of ring current. In fact, the ring current has significant variations with MLT, depending on geomagnetic activity, due to the influence of multiple factors; such as, the partial ring current, region 1/region 2 field-aligned currents, the magnetopause current and sub-storm cycle (magnetotail current). The form of the ring current has been inferred from the three-dimensional distribution of ion differential fluxes from neutral atom imaging; however, this technique can not directly obtain the current density distribution (as can be obtained using multi-spacecraft in situ data). Previous in situ estimates of current density have used: Cluster, THEMIS and other spacecraft groups to study the distribution of the ring current for limited ranges of either radial profile, or MLT and MLAT variations. Here, we report on an extension to these studies using FGM data from MMS obtained during the period September 1, 2015 to December 31, 2016, when the MMS orbit and configuration provided good coverage. We employ the curlometer method to calculate the current density, statistically, to analysis the MLT distribution according to different geomagnetic conditions. Our results show the clear asymmetry of the ring current and its different characteristics under different geomagnetic conditions.</p>

Estimation of the Atlantic inflow through the Strait of Gibraltar from climatological and in situ data

2010 ◽  
Vol 115 (C10) ◽  
Author(s):  
Javier Soto-Navarro ◽  
Francisco Criado-Aldeanueva ◽  
Jesús García-Lafuente ◽  
Antonio Sánchez-Román
Keyword(s):  
Strait Of Gibraltar ◽  
In Situ Data

scholarly journals An Ensemble Kalman Filter with a complex marine ecosystem model: hindcasting phytoplankton in the Cretan Sea

2003 ◽  
Vol 21 (1) ◽  
pp. 399-411 ◽  
Author(s):  
J. I. Allen ◽  
M. Eknes ◽  
G. Evensen
Keyword(s):  
Data Assimilation ◽  
Marine Ecosystem ◽  
Three Dimensional ◽  
Ecosystem Model ◽  
Sequential Data ◽  
Model Errors ◽  
In Situ Data ◽  
Marine Ecosystem Model ◽  
Cretan Sea

Abstract. The purpose of this paper is to examine the use of a complex ecosystem model along with near real-time in situ data and a sequential data assimilation method for state estimation. The ecosystem model used is the European Regional Seas Ecosystem Model (ERSEM; Baretta et al., 1995) and the assimilation method chosen is the Ensemble Kalman Filer (EnKF). Previously, it has been shown that this method captures the nonlinear error evolution in time and is capable of both tracking the observations and providing realistic error estimates for the estimated state. This system has been used to assimilate long time series of in situ chlorophyll taken from a data buoy in the Cretan Sea. The assimilation of this data using the EnKF method results in a marked improvement in the ability of ERSEM to hindcast chlorophyll. The sensitivity of this system to the type of data used for assimilation, the frequency of assimilation, ensemble size and model errors is discussed. The predictability window of the EnKF appears to be at least 2 days. This is an indication that the methodology might be suitable for future operational data assimilation systems using more complex three-dimensional models. Key words. Oceanography: general (numerical modelling; ocean prediction) – Oceanography: biological and chemical (plankton)

scholarly journals Solar wind dynamics around a comet

2018 ◽  
Vol 620 ◽  
pp. A35 ◽  
Author(s):  
E. Behar ◽  
B. Tabone ◽  
M. Saillenfest ◽  
P. Henri ◽  
J. Deca ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Three Dimensional ◽  
Solar Wind Proton ◽  
In Situ Data ◽  
Collisionless Plasmas ◽  
Rosetta Mission ◽  
Proton Dynamics ◽  
Good Agreement

Aims. We aim at analytically modelling the solar wind proton trajectories during their interaction with a partially ionised cometary atmosphere, not in terms of bulk properties of the flow but in terms of single particle dynamics. Methods. We first derive a generalised gyromotion, in which the electric field is reduced to its motional component. Steady-state is assumed, and simplified models of the cometary density and of the electron fluid are used to express the force experienced by individual solar wind protons during the interaction. Results. A three-dimensional (3D) analytical expression of the gyration of two interacting plasma beams is obtained. Applying it to a comet case, the force on protons is always perpendicular to their velocity and has an amplitude proportional to 1/r2. The solar wind deflection is obtained at any point in space. The resulting picture presents a caustic of intersecting trajectories, and a circular region is found that is completely free of particles. The particles do not lose any kinetic energy and this absence of deceleration, together with the solar wind deflection pattern and the presence of a solar wind ion cavity, is in good agreement with the general results of the Rosetta mission. Conclusions. The qualitative match between the model and the in situ data highlights how dominant the motional electric field is throughout most of the interaction region for the solar wind proton dynamics. The model provides a simple general kinetic description of how momentum is transferred between these two collisionless plasmas. It also shows the potential of this semi-analytical model for a systematic quantitative comparison to the data.

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