Detiding Measurement on Transport of the Changjiang-Derived Buoyant Coastal Current

Abstract Measuring the transport of the Changjiang (also known as the Yangtze) River–derived buoyant coastal current, that is, the Min–Zhe Coastal Current, is of great importance for understanding the fate of terrestrial materials from this large river into the open ocean, but it is usually difficult to achieve because of the energetic tidal currents along the Chinese coast. In February 2012, a detiding cruise survey was carried out using the phase-averaging method. For the first time, this coastal current has been quantified with in situ data and has been shown to have a volume transport of 0.215 Sv (1 Sv ≡ 106 m3 s−1) and a maximum surface velocity of ~50 cm s−1. The ratio between the volume transport of the buoyant coastal current and that of the Changjiang is O(10). Freshwater transport by the buoyant coastal current accounts for over 90% of the Changjiang River's discharge. Buoyancy and winds are both important in driving this current.

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A method for monitoring hydrological conditions beneath herbaceous wetlands using multi-temporal ALOS PALSAR coherence data

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xl-7-w4-221-2015 ◽

2015 ◽

Vol XL-7/W4 ◽

pp. 221-226 ◽

Cited By ~ 2

Author(s):

M. Zhang ◽

Z. Li ◽

B. Tian ◽

J. Zhou ◽

J. Zeng

Keyword(s):

Effective Area ◽

Interferometric Synthetic Aperture Radar ◽

Alos Palsar ◽

Hydrological Conditions ◽

In Situ Data ◽

Key Indicator ◽

Multi Temporal ◽

First Time ◽

Good Agreement

Reed marshes, the world’s most widespread type of wetland vegetation, are undergoing major changes as a result of climate changes and human activities. The presence or absence of water in reed marshes has a significant impact on the whole ecosystem and remains a key indicator to identify the effective area of a wetland and help estimate the degree of degeneration. Past studies have demonstrated the use of interferometric synthetic aperture radar (InSAR) to map water-level changes for flooded reeds. However, the identification of the different hydrological states of reed marshes is often poorly understood. The analysis given in this paper shows that L-band interferometric coherence is very sensitive to the water surface conditions beneath reed marshes and so can be used as classifier. A method based on a statistical analysis of the coherence distributions for wet and dry reeds using InSAR pairs was, therefore, investigated in this study. The experimental results were validated by in-situ data and showed very good agreement. This is the first time that information about the water cover under herbaceous wetlands has been derived using interferometric coherence values. This method can also effectively and easily be applied to monitor the hydrological conditions beneath other herbaceous wetlands.

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From zero to infinity: minimum to maximum diversity of the planet by spatio-parametric Rao’s quadratic entropy

10.1101/2021.01.23.427872 ◽

2021 ◽

Author(s):

Duccio Rocchini ◽

Matteo Marcantonio ◽

Daniele Da Re ◽

Giovanni Bacaro ◽

Enrico Feoli ◽

...

Keyword(s):

Satellite Image ◽

Diversity Indices ◽

Spatial Uncertainty ◽

Species Determination ◽

Quadratic Entropy ◽

In Situ Data ◽

Rao’S Quadratic Entropy ◽

Work Done ◽

First Time

AbstractAimThe majority of work done to gather information on Earth diversity has been carried out by in-situ data, with known issues related to epistemology (e.g., species determination and taxonomy), spatial uncertainty, logistics (time and costs), among others. An alternative way to gather information about spatial ecosystem variability is the use of satellite remote sensing. It works as a powerful tool for attaining rapid and standardized information. Several metrics used to calculate remotely sensed diversity of ecosystems are based on Shannon’s Information Theory, namely on the differences in relative abundance of pixel reflectances in a certain area. Additional metrics like the Rao’s quadratic entropy allow the use of spectral distance beside abundance, but they are point descriptors of diversity, namely they can account only for a part of the whole diversity continuum. The aim of this paper is thus to generalize the Rao’s quadratic entropy by proposing its parameterization for the first time.InnovationThe parametric Rao’s quadratic entropy, coded in R, i) allows to represent the whole continuum of potential diversity indices in one formula, and ii) starting from the Rao’s quadratic entropy, allows to explicitly make use of distances among pixel reflectance values, together with relative abundances.Main conclusionsThe proposed unifying measure is an integration between abundance- and distance-based algorithms to map the continuum of diversity given a satellite image at any spatial scale.

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Coastal Current Intrusions from Satellite Altimetry

Remote Sensing ◽

10.3390/rs12223686 ◽

2020 ◽

Vol 12 (22) ◽

pp. 3686

Author(s):

Daniele Casella ◽

Marco Meloni ◽

Anne A. Petrenko ◽

Andrea M. Doglioli ◽

Jerome Bouffard

Keyword(s):

Acoustic Doppler Current Profiler ◽

Point Of View ◽

Ocean Dynamics ◽

False Alarms ◽

Coastal Current ◽

Learning Tools ◽

In Situ Data ◽

Number Of False Alarms ◽

Current Profiler

The use of satellite-based data in coastal regions for the monitoring of fine-scale ocean dynamics, impacting marine ecosystems, is a difficult challenge. A random forest algorithm to detect slope current intrusions into the Gulf of Lion, Mediterranean Sea, has been developed using both improved coastal altimetry data and 10 year-long numerical simulations. The results have been compared to an independent dataset of in situ measurements from a bottom-moored Acoustic Doppler Current Profiler. The algorithm results are very promising: 93% of slope current intrusions have been correctly identified, and the number of false alarms is moderate. The dependence of the algorithm on several environmental factors is discussed in the paper. From the oceanographic point of view, our results confirm the strong impacts of horizontal winds in the dynamic of the intrusion events in the study area. Our methodology combining numerical modeling, in situ data and new machine-learning tools proves effective in improving the capabilities of ocean remote sensing in coastal areas.

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Coronal transients during two solar minima: their source regions and interplanetary counterparts

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004760 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 149-153

Author(s):

Hebe Cremades ◽

Cristina H. Mandrini ◽

Sergio Dasso

Keyword(s):

Solar Corona ◽

Coronal Mass Ejections ◽

Magnetic Clouds ◽

Time Intervals ◽

Solar Source ◽

In Situ Data ◽

Source Regions ◽

Multi Wavelength ◽

First Time

AbstractWe have investigated two full solar rotations belonging to two distinct solar minima, in the frame of two coordinated observational and research campaigns. The nearly uninterrupted gathering of solar coronal data since the beginning of the SOHO era offers the exceptional possibility of comparing two solar minima for the first time, with regard to coronal transients. This study characterizes the variety of outward-travelling transients observed in the solar corona during both time intervals, from very narrow jet-like events to coronal mass ejections (CMEs). Their solar source regions and ensuing interplanetary structures were identified and characterized. Multi-wavelength images from the space missions SOHO, Yohkoh and STEREO, and ground-based observatories were studied for coronal ejecta and their solar sources, while in situ data registered by the ACE spacecraft were inspected for interplanetary CMEs and magnetic clouds. Instrumental aspects such as dissimilar resolution, cadence, and fields of view are considered in order to discern instrumentally-driven disparities from inherent differences between solar minima.

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Downscaling of SMAP Soil Moisture in the Lower Mekong River Basin

Water ◽

10.3390/w12010056 ◽

2019 ◽

Vol 12 (1) ◽

pp. 56 ◽

Cited By ~ 3

Author(s):

Chelsea Dandridge ◽

Bin Fang ◽

Venkat Lakshmi

Keyword(s):

Soil Moisture ◽

Surface Temperature ◽

River Basin ◽

River Basins ◽

Large River ◽

Mekong River ◽

Mekong River Basin ◽

In Situ Data ◽

Large River Basins

In large river basins where in situ data were limited or absent, satellite-based soil moisture estimates can be used to supplement ground measurements for land and water resource management solutions. Consistent soil moisture estimation can aid in monitoring droughts, forecasting floods, monitoring crop productivity, and assisting weather forecasting. Satellite-based soil moisture estimates are readily available at the global scale but are provided at spatial scales that are relatively coarse for many hydrological modeling and decision-making purposes. Soil moisture data are obtained from NASA’s soil moisture active passive (SMAP) mission radiometer as an interpolated product at 9 km gridded resolution. This study implements a soil moisture downscaling algorithm that was developed based on the relationship between daily temperature change and average soil moisture under varying vegetation conditions. It applies a look-up table using global land data assimilation system (GLDAS) soil moisture and surface temperature data, and advanced very high resolution radiometer (AVHRR) and moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) and land surface temperature (LST). MODIS LST and NDVI are used to obtain downscaled soil moisture estimates. These estimates are then used to enhance the spatial resolution of soil moisture estimates from SMAP 9 km to 1 km. Soil moisture estimates at 1 km resolution are able to provide detailed information on the spatial distribution and pattern over the regions being analyzed. Higher resolution soil moisture data are needed for practical applications and modelling in large watersheds with limited in situ data, like in the Lower Mekong River Basin (LMB) in Southeast Asia. The 1 km soil moisture estimates can be applied directly to improve flood prediction and assessment as well as drought monitoring and agricultural productivity predictions for large river basins.

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Validation of INDO12 Ocean Model at Makassar Strait

Omni-Akuatika ◽

10.20884/1.oa.2020.16.2.663 ◽

2020 ◽

Vol 16 (2) ◽

pp. 83

Author(s):

Bayu Priyono ◽

Mukti Trenggono ◽

Teguh Agustiadi

Keyword(s):

Temperature Distribution ◽

Volume Transport ◽

Ocean Model ◽

In Situ Data ◽

Good Comparison ◽

Volume Transports

INDO12, a 1/12 regional configuration of the NEMO3.1 physical ocean model covering the whole Indonesian EEZ has been developed and was running with 3D daily and 2D surface hourly outputs in the framework of the INDESO project. Validate the model results highly required for any downstream applications (services or scientific studies). In order to enhance confidence in using the INDO12 model outputs in Makassar Strait, qualitative comparisons with observed variables is performed. The datasets were used in this study provided by the INSTANT and MITF programs. Validation of model outputs was performed by compare the value of variables from simulation with observation results.The method of comparisons was conducted as follows:current velocities, temperature and salinity, volume transport. The volume transports differences especially occurred below the thermocline layer. The model was colder and fresher in the thermocline layer, whereas deeper the model was warmer and saltier.The differences of the volume transport and temperature distribution affected the transport-weighted temperature and 16°C isotherm depth. The model produced warmer transport-weighted temperature and deeper 16°C isotherm depth compared to the observations. It is concluded from the validation results that the model give a fairly good comparison with the in-situ data, especially for seasonally signals.Keywords: Validation, INDO12, Ocean Model, Makassar Strait, INSTANT and MITF Programe

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Large River Plumes Detection by Satellite Altimetry: Case Study of the Ob–Yenisei Plume

Remote Sensing ◽

10.3390/rs13245014 ◽

2021 ◽

Vol 13 (24) ◽

pp. 5014

Author(s):

Dmitry Frey ◽

Alexander Osadchiev

Keyword(s):

Satellite Altimetry ◽

Outer Boundary ◽

World Ocean ◽

Large River ◽

Statistical Correlation ◽

Surface Salinity ◽

River Plumes ◽

In Situ Data ◽

The World

Satellite altimetry is an efficient instrument for detection dynamical processes in the World Ocean, including reconstruction of geostrophic currents and tracking of mesoscale eddies. Satellite altimetry has the potential to detect large river plumes, which have reduced salinity and, therefore, elevated surface level as compared to surrounding saline sea. In this study, we analyze applicability of satellite altimetry for detection of the Ob–Yenisei plume in the Kara Sea, which is among the largest river plumes in the World Ocean. Based on the extensive in situ data collected at the study area during oceanographic surveys in 2007–2019, we analyze the accuracy and efficiency of satellite altimetry in reproducing, first, the outer boundary of the plume and, second, the internal structure of the plume. We reveal that the value of positive level anomaly within the Ob–Yenisei plume strongly depends on the vertical plume structure and is prone to significant synoptic and seasonal variability due to wind forcing and mixing of the plume with subjacent sea. As a result, despite generally high statistical correlation between the ADT and surface salinity, straightforward usage of ADT for detection of the river plume is incorrect and produces misleading results. Satellite altimetry could provide correct information about spatial extents and shape of the Ob–Yenisei plume only if it is validated by synchronous in situ measurements.

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Evolution of the Freshwater Coastal Current at the Southern Tip of Greenland

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0035.1 ◽

2018 ◽

Vol 48 (9) ◽

pp. 2127-2140 ◽

Cited By ~ 11

Author(s):

Peigen Lin ◽

Robert S. Pickart ◽

Daniel J. Torres ◽

Astrid Pacini

Keyword(s):

Velocity Structure ◽

Greenland Ice Sheet ◽

Volume Transport ◽

The Arctic ◽

Labrador Sea ◽

Coastal Current ◽

Velocity Measurements ◽

The West ◽

West Side ◽

Freshwater Transport

AbstractShipboard hydrographic and velocity measurements collected in summer 2014 are used to study the evolution of the freshwater coastal current in southern Greenland as it encounters Cape Farewell. The velocity structure reveals that the coastal current maintains its identity as it flows around the cape and bifurcates such that most of the flow is diverted to the outer west Greenland shelf, while a small portion remains on the inner shelf. Taking into account this inner branch, the volume transport of the coastal current is conserved, but the freshwater transport decreases on the west side of Cape Farewell. A significant amount of freshwater appears to be transported off the shelf where the outer branch flows adjacent to the shelfbreak circulation. It is argued that the offshore transposition of the coastal current is caused by the flow following the isobaths as they bend offshore because of the widening of the shelf on the west side of Cape Farewell. An analysis of the potential vorticity shows that the subsequent seaward flux of freshwater can be enhanced by instabilities of the current. This set of circumstances provides a pathway for the freshest water originating from the Arctic, as well as runoff from the Greenland ice sheet, to be fluxed into the interior Labrador Sea where it could influence convection in the basin.

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Probing the Dynamic Self-Assembly Behaviour of Photoswitchable Wormlike Micelles in Real Time

10.26434/chemrxiv.7098695 ◽

2018 ◽

Author(s):

Elaine A. Kelly ◽

Judith E. Houston ◽

Rachel Evans

Keyword(s):

Real Time ◽

Absorption Spectroscopy ◽

Self Assembly ◽

Uv Light ◽

Wormlike Micelles ◽

Tetraethylene Glycol ◽

Light Illumination ◽

First Time ◽

Dependent Processes

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such asdrug delivery and micellar catalysis. Currently, their behaviour in the equilibrium cis-and trans-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, <a>tetraethylene glycol mono(4′,4-octyloxy,octyl-azobenzene) </a>(C8AzoOC8E4) using small-angle neutron scattering (SANS). We show that the incorporation of in-situUV-Vis absorption spectroscopy with SANS allows the scattering profile, and hence micelle shape, to be correlated with the extent of photoisomerisation in real-time. It was observed that C8AzoOC8E4could switch between wormlike micelles (transnative state) and fractal aggregates (under UV light), with changes in the self-assembled structure arising concurrently with changes in the absorption spectrum. Wormlike micelles could be recovered within 60 seconds of blue light illumination. To the best of our knowledge, this is the first time the degree of AzoPS photoisomerisation has been tracked in-situthrough combined UV-Vis absorption spectroscopy-SANS measurements. This technique could be widely used to gain mechanistic and kinetic insights into light-dependent processes that are reliant on self-assembly.

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The Total Synthesis of Rhabdastrellic Acid A

10.26434/chemrxiv.7479944 ◽

2018 ◽

Author(s):

Yaroslav Boyko ◽

Christopher Huck ◽

David Sarlah

Keyword(s):

Total Synthesis ◽

Late Stage ◽

Cross Coupling ◽

Side Chains ◽

General Strategy ◽

Modular Approach ◽

Linear Sequence ◽

Generating Sequence ◽

First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained trans-syn-trans-perhydrobenz[e]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a p-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

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