Response of a Small River Plume on Wind Forcing

Wind forcing is the main driver of river plume dynamics. Direction and magnitude of wind determine position, shape, and size of a river plume. The response of river plumes on wind forcing was simulated in many numerical modeling studies; however, in situ measurements of this process are still very scarce. In this study, we report the first direct measurements of frontal movement of a small river plume under variable wind forcing conditions. Using quadcopters, we performed nearly continuous daytime aerial observations of the Bzyb river plume located in the non-tidal Black Sea. The aerial remote sensing was accompanied by synchronous in situ measurements of wind forcing. We assessed spreading patterns of the plume and evaluated movement velocity of its outer border with unprecedentedly high spatial (∼10 m) and temporal (∼1 min) resolution, which was not available in previous studies based on in situ measurements and satellite observations. Based on the collected data, we evaluated the time of response of plume spreading dynamics on changes in wind forcing conditions. The advection velocity of the outer plume border shows linear relation to wind speed with very small response time (10–20 min). The reversal between upstream/downstream plume spreading occurs during several hours under moderate wind forcing conditions. These reversals involve only near-field part of the plume, which cause detachment of the far-field part of the plume. The obtained results are crucial for understanding and simulating spreading dynamics of small river plumes worldwide.

Download Full-text

Spatial structure, temporal variability, and dynamical features of small river plumes observed by aerial drones

10.5194/egusphere-egu2020-13161 ◽

2020 ◽

Author(s):

Alexander Osadchiev ◽

Alexandra Barymova

Keyword(s):

Spatial Structure ◽

Internal Waves ◽

Temporal Variability ◽

Outer Part ◽

River Estuary ◽

River Plume ◽

Small River ◽

River Plumes ◽

Dynamical Features

<p>We use optical imagery and video of ocean surface acquired from aerial drones (quadcopters) to study small river plumes formed in the northeastern part of the Black Sea. Quadcopters can continuously observe small river plumes with high spatial resolution from relatively low altitude. It provides unprecedented ability to study spatial structure of small river plumes, detect and measure their temporal variability, register various dynamical features of these plumes. In this work we describe and analyze strongly inhomogeneous structure of small river plumes manifested by complex and dynamically active internal frontal zones; undulate form of sharp front between small river plume and ambient sea and energetic lateral mixing across this front caused by frontal baroclinic instability; internal waves generated by river discharge near a river estuary and propagating within inner part of a plume; internal waves generated by vortex circulation of a river plume and propagating within outer part of a plume. The issues reported in this study remained mainly unaddressed before due to low spatial and/or temporal resolution of in situ measurements and satellite imagery used in previous related studies. We show that usage of aerial drones, first, strongly enhance in situ and satellite observations of structure and variability of small plumes, second, provides ability to perform accurate, continuous, and high-resolution measurements of their spatial characteristics and current velocity fields and, finally, significantly improves organization of operational field measurements. As a result, aerial drones are effective tools to obtain new qualitative insights and quantitative assessments of structure, variability, and dynamics of small river plumes.</p>

Download Full-text

Spreading dynamics of small river plumes off the northeastern coast of the Black Sea observed by Landsat 8 and Sentinel-2

Remote Sensing of Environment ◽

10.1016/j.rse.2018.11.043 ◽

2019 ◽

Vol 221 ◽

pp. 522-533 ◽

Cited By ~ 14

Author(s):

Alexander Osadchiev ◽

Roman Sedakov

Keyword(s):

Black Sea ◽

Small River ◽

The Black Sea ◽

Landsat 8 ◽

River Plumes ◽

Spreading Dynamics ◽

Northeastern Coast ◽

Sentinel 2

Download Full-text

Spatial Structure, Short-temporal Variability, and Dynamical Features of Small River Plumes as Observed by Aerial Drones: Case Study of the Kodor and Bzyp River Plumes

Remote Sensing ◽

10.3390/rs12183079 ◽

2020 ◽

Vol 12 (18) ◽

pp. 3079 ◽

Cited By ~ 1

Author(s):

Alexander Osadchiev ◽

Alexandra Barymova ◽

Roman Sedakov ◽

Roman Zhiba ◽

Roman Dbar

Keyword(s):

Temporal Variability ◽

In Situ Measurements ◽

Small River ◽

The Black Sea ◽

River Plumes ◽

Spatial And Temporal Scales ◽

Coastal Sea ◽

Lateral Mixing ◽

First Time

Quadcopters can continuously observe ocean surface with high spatial resolution from relatively low altitude, albeit with certain limitations of their usage. Remote sensing from quadcopters provides unprecedented ability to study small river plumes formed in the coastal sea. The main goal of the current work is to describe structure and temporal variability of small river plumes on small spatial and temporal scales, which are limitedly covered by previous studies. We analyze optical imagery and video records acquired by quadcopters and accompanied by synchronous in situ measurements and satellite observations within the Kodor and Bzyp plumes, which are located in the northeastern part of the Black Sea. We describe extremely rapid response of these river plume to energetic rotating coastal eddies. We reveal several types of internal waves within these river plumes, measure their spatial and dynamical characteristics, and identify mechanisms of their generation. We suggest a new mechanism of formation of undulate fronts between small river plumes and ambient sea, which induces energetic lateral mixing across these fronts. The results reported in this study are addressed for the first time as previous related works were mainly limited by low spatial and/or temporal resolution of in situ measurements and satellite imagery.

Download Full-text

Internal Waves as a Source of Concentric Rings within Small River Plumes

Remote Sensing ◽

10.3390/rs13214275 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4275

Author(s):

Alexander Osadchiev ◽

Roman Sedakov ◽

Alexandra Gordey ◽

Alexandra Barymova

Keyword(s):

Remote Sensing ◽

Internal Waves ◽

High Frequency ◽

River Mouth ◽

Small River ◽

Shear Instability ◽

Joint Analysis ◽

The Black Sea ◽

River Plumes

This study is focused on concentric rings, which are regularly observed by remote sensing of small river plumes located in different regions worldwide. We report new aerial observations of these features obtained by quadcopters and supported by synchronous in situ measurements, which were collected during the recent field survey at the Bzyb river plume in the eastern part of the Black Sea. Joint analysis of remote sensing imagery and in situ data suggest that the observed concentric rings are surface manifestations of high-frequency internal waves generated in the vicinity of the river mouth. The obtained results demonstrate that the propagation of these waves does not induce offshore material transport within the plume induced by shear instability, which was hypothesized in a recent numerical modeling study of this process. We provide an explanation for the appearance of misleading material features in the numerical simulations discussed above. Finally, we discuss directions for future research of high-frequency internal waves generated in small river plumes.

Download Full-text

The Congo River plume: Impact of the forcing on the far‐field and near‐field dynamics

Journal of Geophysical Research Oceans ◽

10.1002/jgrc.20062 ◽

2013 ◽

Vol 118 (2) ◽

pp. 964-989 ◽

Cited By ~ 26

Author(s):

Cléa Denamiel ◽

W. Paul Budgell ◽

Ralf Toumi

Keyword(s):

Near Field ◽

River Plume ◽

Far Field ◽

Congo River

Download Full-text

Emissions and Noise Pollution Diagnosis of a Turbogas Power Plant During Commissioning Service

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-23671 ◽

2010 ◽

Cited By ~ 1

Author(s):

Norberto Pe´rez Rodri´guez ◽

Erik Rosado Tamariz ◽

Rafael Garci´a Illescas

Keyword(s):

Power Plant ◽

Cooling System ◽

Near Field ◽

Noise Pollution ◽

Point Of View ◽

International Standards ◽

Partial Load ◽

The City ◽

Permissible Deviation

This work is focused on the diagnosis of behavior, from the point of view of control emissions and noise level, of a power Turbogas plant during the process of commissioning, to guarantee that its operation complies with national and international standards. The environmental diagnosis of the power plant was developed as part of the performance evaluation of the unit. The conditions of the unit evaluation include operation at base load and partial load, as well as time periods for load changes. The evaluated power plant consists of an aeroderivative gas turbine installed in a simple cycle, operating with a cooling system (chiller) installed in the urban zone of Mexico City. Therefore, it should comply with the legislation and regulations of the city concerning air pollution and allowed noise, besides the international standards established by the manufacturer. The study includes emissions measurements using a Continuous Emissions Monitoring System installed in-situ, previously calibrated and checked during and after the test which was found inside the permissible deviation of 3%. Measurements were recorded at intervals of 5 minutes during test periods of 110 minutes for each load and 45 minutes for load changes. On the other hand, noise pressure evaluation was carried out in near field as well as far field produced by the power plant during operation. Measurements were carried out by using precision instruments installed specifically for it. A temporary system for obtaining data was used to monitoring the environmental conditions every 30 seconds. It was possible to verify that the turbogenerator complies with all noise levels and contaminant emissions requirements and regulations according to the limits established by the manufacturer and national and international standards.

Download Full-text

In-situ lateral fabrication of zinc and aluminum nanodots by near field optical chemical vapor deposition

Technical Digest. CLEO/Pacific Rim 2001. 4th Pacific Rim Conference on Lasers and Electro-Optics (Cat. No.01TH8557) ◽

10.1109/cleopr.2001.967953 ◽

2002 ◽

Cited By ~ 1

Author(s):

Y. Yamamoto ◽

T. Kawazoe ◽

G.H. Lee ◽

T. Shimizu ◽

M. Kourogi ◽

...

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Near Field ◽

Chemical Vapor

Download Full-text

Plasmalemma Invaginations as Characteristic Constituents of Plasmodia of Physarum Polycephalum

Journal of Cell Science ◽

10.1242/jcs.16.1.23 ◽

1974 ◽

Vol 16 (1) ◽

pp. 23-37

Author(s):

K. E. WOHLFARTH-BOTTERMANN

Keyword(s):

Physarum Polycephalum ◽

Close Contact ◽

Surrounding Medium ◽

Defined Medium ◽

Subsequent Paper ◽

Outer Border ◽

Shuttle Streaming ◽

Food Absorption ◽

Plasmalemma Invaginations

Plasmodia of Physarum polycephalum grown on agar or filter paper and fed with rolled oats as food or with a partially defined medium were morphologically analysed in the living state and after fixation. Observation of the living plasmodium growing on agar reveals plasmalemma indentations in the outer regions of protoplasmic strands, which were studied in more detail by phase-contrast microscopy of unstained 1-µm sections. Plasmodia fixed and embedded in situ, i.e. in close contact to their substrate, exhibit an extensive system of plasmalemma invaginations as characteristic constituents throughout all regions. In plasmodial strands measuring between 40 µm and 1.5 mm in diameter and involved in shuttle streaming, the plasmalemma invaginations are found within the outer ectoplasmic wall. Rounded-up parts of this branched extracellular labyrinth limit the endoplasmic core engaged in the mass transport of protoplasm by shuttle streaming. Despite this clearcut borderline, the central endoplasmic core and the ectoplasmic cortex are connected by occasional protoplasmic bridges. The extracellular phase within the ectoplasmic regions of the strands can be interpreted either as a result of plasmalemma invaginations from the outer border of the strand, or as a consequence of pseudopodial-like processes originating from the central core and extending into the surrounding medium. The invagination system provides an extensive enlargement of the surface area within the multinucleate protoplasmic mass, probably important for food absorption, excretion processes and motility phenomena. In thick protoplasmic strands with diameters between 0.2 and 1.5 mm, there is an intimate connexion between the actomyosin fibrils and the invagination system. The fibrils are attached to the plasmalemma invaginations and/or run parallel to the invaginated plasmalemma sheets. The close relations between the invagination system and actomyosin fibrils will be described in detail in a subsequent paper.

Download Full-text

Study on the Properties of Aerodynamic Reference Sound Sources

Acta Acustica united with Acustica ◽

10.3813/aaa.919377 ◽

2019 ◽

Vol 105 (6) ◽

pp. 960-969 ◽

Cited By ~ 1

Author(s):

Spyros Brezas ◽

Volker Wittstock

Keyword(s):

Ambient Temperature ◽

Atmospheric Pressure ◽

Rotation Speed ◽

Near Field ◽

Sound Power ◽

Sound Sources ◽

The Core ◽

In Situ Conditions ◽

Calibration Condition

Towards the establishment of traceability in sound power in airborne sound, the present study focuses on the dissemination procedure. Aerodynamic reference sound sources were studied as potential transfer standards. Initially, the sources were examined in the up-to-present requirements. The core of the study is the correction required for the transition from calibration to in situ conditions. The influence of atmospheric pressure, ambient temperature and fan rotation speed was investigated and the corresponding correction was determined. A comparison to an existing correction was also performed. Near field effects were another part of the study. The related uncertainty was estimated in a transparent approach. The dependency of the uncertainty on the in situ and calibration condition values is also presented.

Download Full-text