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

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.

Download Full-text

Gas Phase and Surface Reactions in Mocvd of GaAs from Triethylgallium, Trimethylgallium, and Organometallic Arsenic Precursors

MRS Proceedings ◽

10.1557/proc-131-103 ◽

1988 ◽

Vol 131 ◽

Author(s):

Thomas R. Omstead ◽

Penny M. Van Sickle ◽

Klavs F. Jensen

Keyword(s):

Gas Phase ◽

Low Temperatures ◽

Surface Reactions ◽

Rate Data ◽

Gas Phase Reactions ◽

Heated Zone ◽

Model Predictions ◽

First Time ◽

Good Agreement

ABSTRACTThe growth of GaAs from triethylgallium (TEG) and trimethylgallium (TMG) with tertiarybutylarsine (tBAs), triethylarsenic (TEAs), and trimethylarsenic (TMAs), has been investigated by using a reactor equipped with a recording microbalance for in situ rate measurements. Rate data show that the growth with these precursors is dominated by the formation of adduct compounds in the gas lines, by adduct related parasitic gas phase reactions in the heated zone, and by the surface reactions. A model is proposed for the competition between deposition reactions and the parasitic gas phase reactions. Model predictions are in very good agreement with experimental data for all combinations of precursors except for TEG/TMAs where extensive gallium droplet formation is observed at low temperatures. Growth of reasonable quality GaAs with Hall mobilities of 7600 cm2/Vs at 77 K using TEG and tBAs is reported for the first time.

Download Full-text

Tracer Stirring around a Meddy: The Formation of Layering

Journal of Physical Oceanography ◽

10.1175/jpo-d-14-0061.1 ◽

2015 ◽

Vol 45 (2) ◽

pp. 407-423 ◽

Cited By ~ 22

Author(s):

Thomas Meunier ◽

Claire Ménesguen ◽

Richard Schopp ◽

Sylvie Le Gentil

Keyword(s):

Vortex Core ◽

Azimuthal Velocity ◽

Thin Layers ◽

Vertical Shear ◽

In Situ Data ◽

Simple Scaling ◽

Diffusive Processes ◽

Tracer Experiments ◽

Good Agreement

AbstractThe dynamics of the formation of layering surrounding meddy-like vortex lenses is investigated using primitive equation (PE), quasigeostrophic (QG), and tracer advection models. Recent in situ data inside a meddy confirmed the formation of highly density-compensated layers in temperature and salinity at the periphery of the vortex core. Very high-resolution PE modeling of an idealized meddy showed the formation of realistic layers even in the absence of double-diffusive processes. The strong density compensation observed in the PE model, in good agreement with in situ data, suggests that stirring might be a leading process in the generation of layering. Passive tracer experiments confirmed that the vertical variance cascade in the periphery of the vortex core is triggered by the vertical shear of the azimuthal velocity, resulting in the generation of thin layers. The time evolution of this process down to scales of O(10) m is quantified, and a simple scaling is proposed and shown to describe precisely the thinning down of the layers as a function of the initial tracer column’s horizontal width and the vertical shear of the azimuthal velocity. Nonlinear QG simulations were performed and analyzed for comparison with the work of Hua et al. A step-by-step interpretation of these results on the evolution of layering is proposed in the context of tracer stirring.

Download Full-text

CAUSAL FREQUENCY-LINEAR ATTENUATION ALGORITHM FOR TIME DOMAIN PROBLEMS

Journal of Computational Acoustics ◽

10.1142/s0218396x09003987 ◽

2009 ◽

Vol 17 (04) ◽

pp. 357-364

Author(s):

B. EDWARD MCDONALD

Keyword(s):

Wave Propagation ◽

Time Domain ◽

Fourier Transforms ◽

Phase Speed ◽

Sandy Sediment ◽

Acoustic Wave Propagation ◽

In Situ Data ◽

Ocean Sediment ◽

Good Agreement

Attenuation which is linear in frequency (as opposed to quadratic as for laminar viscosity) occurs in porous media wave propagation and biomedical applications. Straightforward use of Fourier transforms for frequency-linear attenuation violates causality. We give a causal time domain algorithm with numerical stability criteria and verify its accuracy. For acoustic wave propagation in ocean sediment, the algorithm results in a mild increase of phase speed with frequency as a result of the Kramers–Kronig relation. The algorithm gives results in good agreement with in situ data for sandy sediment.

Download Full-text

Estimation of ship emission rates at a major shipping lane by long path DOAS measurements

10.5194/amt-2021-65 ◽

2021 ◽

Author(s):

Kai Krause ◽

Folkard Wittrock ◽

Andreas Richter ◽

Stefan Schmitt ◽

Denis Pöhler ◽

...

Keyword(s):

Emission Factors ◽

Emission Rates ◽

River Elbe ◽

Gaussian Plume ◽

Remote Sensing Techniques ◽

One Year ◽

First Time ◽

Good Agreement ◽

Ship Emission

Abstract. Ships are an important source of SO2 and NOx, which are key parameters of air quality. Monitoring of ship emissions is usually carried out using in situ instruments on land, which depend on favourable wind conditions to transport the emitted substances to the measurement site. Remote sensing techniques such as long path DOAS (LP-DOAS) measurements can supplement those measurements, especially in unfavourable meteorological conditions. In this study one year of LP-DOAS measurements made across the river Elbe close to Hamburg (Germany) have been evaluated. Peaks (i.e. elevated concentrations) in the NO2 and SO2 time series were assigned to passing ships and a method to derive emission rates of SO2, NO2 and NOx from those measurements using a Gaussian plume model is presented. 7402 individual ship passages have been monitored and their respective NOx, SO2 and NO2 emission rates have been derived. The emission rates, coupled with the knowledge of the ship type, ship size and ship speed have been analysed. Emission rates are compared to emission factors from previous studies and show good agreement. In contrast to emission factors (in gram per kilogram fuel) the derived emission rates (in gram per second) do not need further knowledge about the fuel consumption of the ship. To our knowledge this is the first time emission rates of air pollutants from individual ships have been derived from LP-DOAS measurements.

Download Full-text

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.

Download Full-text

Estimation of ship emission rates at a major shipping lane by long-path DOAS measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-14-5791-2021 ◽

2021 ◽

Vol 14 (8) ◽

pp. 5791-5807

Author(s):

Kai Krause ◽

Folkard Wittrock ◽

Andreas Richter ◽

Stefan Schmitt ◽

Denis Pöhler ◽

...

Keyword(s):

Emission Factors ◽

Optical Absorption Spectroscopy ◽

Emission Rates ◽

River Elbe ◽

Gaussian Plume ◽

Remote Sensing Techniques ◽

First Time ◽

Good Agreement ◽

Ship Emission

Abstract. Ships are an important source of SO2 and NOx, which are key parameters of air quality. Monitoring of ship emissions is usually carried out using in situ instruments on land, which depend on favourable wind conditions to transport the emitted substances to the measurement site. Remote sensing techniques such as long-path differential optical absorption spectroscopy (LP-DOAS) measurements can supplement those measurements, especially in unfavourable meteorological conditions. In this study 1 year of LP-DOAS measurements made across the river Elbe close to Hamburg (Germany) have been evaluated. Peaks (i.e. elevated concentrations) in the NO2 and SO2 time series were assigned to passing ships, and a method to derive emission rates of SO2, NO2 and NOx from those measurements using a Gaussian plume model is presented. A total of 7402 individual ship passages have been monitored, and their respective NOx, SO2 and NO2 emission rates have been derived. The emission rates, coupled with the knowledge of the ship type, ship size and ship speed, have been analysed. Emission rates are compared to emission factors from previous studies and show good agreement. In contrast to emission factors (in grams per kilogram fuel), the derived emission rates (in grams per second) do not need further knowledge about the fuel consumption of the ship. To our knowledge this is the first time emission rates of air pollutants from individual ships have been derived from LP-DOAS measurements.

Download Full-text

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.

Download Full-text

Detecting the landslide vulnerability in the epicentre of Wenchuan Earthquake via SBAS-InSAR method

10.5194/egusphere-egu2020-3907 ◽

2020 ◽

Author(s):

Wenjiang Zhang

Keyword(s):

Wenchuan Earthquake ◽

Soil Layer ◽

In Situ Monitoring ◽

Ground Subsidence ◽

In Situ Observation ◽

Interferometric Synthetic Aperture Radar ◽

Multi Temporal ◽

Sbas Insar ◽

River Valleys

Valleys in the epicentre of Wenchuan Earthquake (Sichuan Province, China) are severely subjected to landside risks partially due to the persistent influences of the serious earthquake in 2008. Without enough regionally in-situ monitoring measures, the method of multi-temporal, differential interferometric synthetic aperture radar (D-InSAR) provides an efficient to monitor the surface subsidence and thus the landslide vulnerability. In this&#160;study,&#160;we used the Sentinel Satellite Images (2015-2018) to extract the subsidence information along river valleys near the Wenchuan Earth epicentre, which was well validated by the in-situ observation of one GPS station (RSME=1.6 cm, p<0.01). Our results showed the persistent ground subsidence (1.5 mm yr-1, p<0.01) at many places, which was also related to terrain aspect besides to the well-proved conditions of slope, vegetation cover and soil layer. This fact that implied the terrain aspect should be taken into accounts in landside vulnerability analyses, because precipitation is locally more abundant in windward places. Results emphasized the higher vulnerability of landslide in summer, which could be attributed to more precipitation during summer in the study area. Our study extracted over 100-km valleys (and especially ~50 places) with high landslide vulnerability (subsidence rate > 1.20 mm yr-1), which should be paid high-prior careful attentions so as to avoid potential geological disasters.

Download Full-text

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

Remote Sensing Letters ◽

10.1080/2150704x.2015.1066520 ◽

2015 ◽

Vol 6 (8) ◽

pp. 618-627 ◽

Cited By ~ 10

Author(s):

Meimei Zhang ◽

Zhen Li ◽

Bangsen Tian ◽

Jianmin Zhou ◽

Jiangyuan Zeng

Keyword(s):

Alos Palsar ◽

Hydrological Conditions ◽

Multi Temporal

Download Full-text

Problems with the retrieval of glacier net surface balance from SAR imagery

Annals of Glaciology ◽

10.3189/172756405781812736 ◽

2005 ◽

Vol 42 ◽

pp. 209-216 ◽

Cited By ~ 1

Author(s):

Ian A. Brown ◽

Per Klingbjer ◽

Andy Dean

Keyword(s):

Mass Balance ◽

Glacier Mass Balance ◽

In Situ Data ◽

Amplitude Data ◽

Multi Temporal ◽

Geophysical Processes ◽

Sar Imagery ◽

Arctic Glacier ◽

Surface Balance

AbstractThere are relatively few comparisons between synthetic aperture radar (SAR) observations and glacier mass-balance measurements. More typically, SAR has been deployed to identify changes in the end-of-summer snowline and other facies boundaries. In this paper, we analyze the geophysical processes affecting SAR amplitude data over two Arctic glacier systems in northern Scandinavia to assess the potential of SAR observations for the retrieval of surface balance parameters. Using a backscatter model and in situ data, we identify the controls on SAR imagery in terms of mass-balance measurement and discuss the glaciological parameters which can reasonably be derived from multi-temporal SAR data. Our results show that amplitude SAR imagery, in the absence of in situ measurements, is not capable of providing meaningful mass-balance data. We show that backscatter from temperate glaciers is affected primarily by snow grain-size and density, and therefore processes such as firnification or depth-hoar formation can complicate the analysis of imagery. We conclude that SAR imagery over temperate glaciers can provide valuable proxy information but not direct mass-balance terms.

Download Full-text