scholarly journals Optimal ash particle refractive index model for simulating the brightness temperature spectrum of volcanic ash clouds from satellite infrared sounder measurements

2021 ◽  
Author(s):  
Hiroshi Ishimoto ◽  
Masahiro Hayashi ◽  
Yuzo Mano
Keyword(s):  
Refractive Index ◽  
Brightness Temperature ◽  
Volcanic Ash ◽  
Satellite Measurements ◽  
Temperature Spectrum ◽  
Index Model ◽  
Rock Types ◽  
Volcanic Events ◽  
Atmospheric Sounding ◽  
Using Data

Abstract. Using data from the Infrared Atmospheric Sounding Interferometer (IASI) measurements of volcanic ash clouds and radiative transfer calculations, we identify the optimal refractive index model for simulating the measured brightness temperature spectrum of volcanic ash material. We assume that the optimal refractive index model has the smallest root mean square of the brightness temperature difference between measurements and simulations for channels in the wavenumber range of 750–1400 cm−1 and compare 21 refractive index models for optical properties of ash particles, including recently published models. From the results of numerical simulations for 164 pixels of IASI measurements for ash clouds from 11 volcanoes, we found that the measured brightness temperature spectrum could be well simulated using certain newly established refractive index models. In the cases of Eyjafjallajökull and Grímsvötn ash clouds, the optimal refractive index models determined through numerical simulation correspond to those deduced from the chemical composition of ash samples for the same volcanic eruption events. This finding suggests that infrared sounder measurement of volcanic ash clouds is an effective approach to estimating the optimal refractive index model. However, discrepancies between the estimated refractive index models based on satellite measurements and the associated volcanic rock types were observed for some volcanic events.

scholarly journals An effective method for the detection of trace species demonstrated using the MetOp Infrared Atmospheric Sounding Interferometer

2010 ◽  
Vol 3 (5) ◽  
pp. 4531-4569
Author(s):  
J. C. Walker ◽  
A. Dudhia ◽  
E. Carboni
Keyword(s):  
Brightness Temperature ◽  
Sulphur Dioxide ◽  
Atmospheric Temperature ◽  
Quantitative Information ◽  
Low Noise ◽  
Target Species ◽  
Trace Species ◽  
Atmospheric Sounding ◽  
The Difference ◽  
Using Data

Abstract. A detection method is demonstrated for volcanic sulphur dioxide and ammonia from agriculture using data from the MetOp Infrared Atmospheric Sounding Interferometer (IASI). The method is an extension of the Brightness Temperature Difference (BTD) technique which uses the difference in brightness temperature between a small number of channels sensitive to the target species and spectral background to determine the presence of the target species. The method described here allows instead for the use of large numbers of channels with an optimal set of linear weights which effectively suppress the spectral background allowing low-noise filters to be produced which are capable of distinguishing the target species from other parameters such as interfering species, surface and atmospheric temperature, and cloudiness without retrieving these parameters explicitly. Once generated, the filters can be applied quickly and easily to identify events of interest over a large global dataset, in near-real-time if required, and in some circumstances a degree of quantitative information can be extracted about the abundance of the target species. The theory behind the generation of the filters is first described. The filters are then used in the detection of volcanic sulphur dioxide from the eruption of the Kasatochi volcano in Alaska, beginning in August 2008, and in the detection of ammonia emissions related to agriculture over Southern Asia in May 2008. The performance of new the filters is compared against that obtained using existing filters.

scholarly journals Optimising the Complex Refractive Index Model for Estimating the Permittivity of Heterogeneous Concrete Models

2021 ◽  
Vol 13 (4) ◽  
pp. 723
Author(s):  
Hossain Zadhoush ◽  
Antonios Giannopoulos ◽  
Iraklis Giannakis
Keyword(s):  
Refractive Index ◽  
Shape Factor ◽  
Complex Refractive Index ◽  
Fdtd Method ◽  
Air Voids ◽  
Water Fraction ◽  
Index Model ◽  
General Complex ◽  
Ground Penetrating ◽  
Fine Tune

Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.

Solid–liquid–liquid phase envelopes from temperature-scanned refractive index data

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alcides J. Sitoe ◽  
Franco Pretorius ◽  
Walter W. Focke ◽  
René Androsch ◽  
Elizabeth L. du Toit
Keyword(s):  
Refractive Index ◽  
Liquid Phase ◽  
Volume Fraction ◽  
Solution Temperature ◽  
Linear Behavior ◽  
Upper Critical Solution Temperature ◽  
Novel Method ◽  
Using Data ◽  
Solid Liquid ◽  
Liquid Liquid Phase Separation

Abstract A novel method for estimating the upper critical solution temperature (UCST) of N,N-diethyl-m-toluamide (DEET)-polyethylene systems was developed. It was validated using data for the dimethylacetamide (DMA)-alkane systems which showed that refractive index mixing rules, linear in volume fraction, can accurately predict mixture composition for amide-alkane systems. Furthermore, rescaling the composition descriptor with a single adjustable parameter proved adequate to address any asymmetry when modeling the DMA-alkane phase envelopes. This allowed the translation of measured refractive index cooling trajectories of DEET-alkane systems into phase diagrams and facilitated the estimation of the UCST values by fitting the data with an adjusted composition descriptor model. For both the DEET- and DMA-alkane systems, linear behavior of UCST values in either the Flory–Huggins critical interaction parameter, or the alkane critical temperature, with increasing alkane molar mass is evident. The UCST values for polymer diluent systems were estimated by extrapolation using these two complimentary approaches. For the DEET-polyethylene system, values of 183.4 and 180.1 °C respectively were obtained. Both estimates are significantly higher than the melting temperature range of polyethylene. Initial liquid–liquid phase separation is therefore likely to be responsible for the previously reported microporous microstructure of materials formed from this binary system.

scholarly journals Data assimilation for volcanic ash plumes using a satellite observational operator: a case study on the 2010 Eyjafjallajökull volcanic eruption

2017 ◽  
Vol 17 (2) ◽  
pp. 1187-1205 ◽  
Author(s):  
Guangliang Fu ◽  
Fred Prata ◽  
Hai Xiang Lin ◽  
Arnold Heemink ◽  
Arjo Segers ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Volcanic Ash ◽  
Three Dimensional ◽  
Forecast Accuracy ◽  
Improve Model ◽  
Powerful Approach ◽  
Using Data ◽  
D Model

Abstract. Using data assimilation (DA) to improve model forecast accuracy is a powerful approach that requires available observations. Infrared satellite measurements of volcanic ash mass loadings are often used as input observations for the assimilation scheme. However, because these primary satellite-retrieved data are often two-dimensional (2-D) and the ash plume is usually vertically located in a narrow band, directly assimilating the 2-D ash mass loadings in a three-dimensional (3-D) volcanic ash model (with an integral observational operator) can usually introduce large artificial/spurious vertical correlations.In this study, we look at an approach to avoid the artificial vertical correlations by not involving the integral operator. By integrating available data of ash mass loadings and cloud top heights, as well as data-based assumptions on thickness, we propose a satellite observational operator (SOO) that translates satellite-retrieved 2-D volcanic ash mass loadings to 3-D concentrations. The 3-D SOO makes the analysis step of assimilation comparable in the 3-D model space.Ensemble-based DA is used to assimilate the extracted measurements of ash concentrations. The results show that satellite DA with SOO can improve the estimate of volcanic ash state and the forecast. Comparison with both satellite-retrieved data and aircraft in situ measurements shows that the effective duration of the improved volcanic ash forecasts for the distal part of the Eyjafjallajökull volcano is about 6 h.

scholarly journals Optical, microphysical and compositional properties of the Eyjafjallajökull volcanic ash

2014 ◽  
Vol 14 (9) ◽  
pp. 13271-13300 ◽  
Author(s):  
A. Rocha-Lima ◽  
J. V. Martins ◽  
L. A. Remer ◽  
N. A. Krotkov ◽  
M. H. Tabacniks ◽  
...  
Keyword(s):  
Refractive Index ◽  
Volcanic Ash ◽  
Fine Particles ◽  
Absorption Efficiency ◽  
Particle Sizes ◽  
Air Volume ◽  
Automatic Software ◽  
Compositional Properties ◽  
Size Distribution Of Particles ◽  
Mass Absorption Efficiency

Abstract. Microphysical, optical, and compositional properties of the volcanic ash from the April–May (2010) Eyjafjallajökull volcanic eruption are presented. Samples of the volcanic ash were taken on the ground in the vicinity of the volcano. The material was sieved, re-suspended, and collected on filters, separating particle sizes into coarse and fine modes. The spectral mass absorption efficiency αabs [m2 g−1] was determined for coarse and fine particles in the wavelength range from 300 to 2500 nm. Size distribution of particles on filters was obtained using a semi-automatic software to analyze images obtained by Scanning Electron Microscopy (SEM). The grain density of the volcanic ash was determined as 2.16(13) g cm−3 by measuring the variation of air volume in a system with volcanic ash and air under compression. Using Mie–Lorenz and T-matrix theories, the imaginary part of the refractive index was derived. Results show the spectral imaginary refractive index ranging from 0.001 to 0.005. Fine and coarse particles were analyzed by X-Ray fluorescence for elemental composition. Fine and coarse mode particles exhibit distinct compositional and optical differences.

Variation of Quiet Sun Radiation during Solar Cycles 23 and 24

2017 ◽  
Vol 13 (S335) ◽  
pp. 11-13
Author(s):  
Mahender Aroori ◽  
G. Yellaiah ◽  
K. Chenna Reddy
Keyword(s):  
Radio Emission ◽  
Brightness Temperature ◽  
Statistical Method ◽  
Solar Radio ◽  
Solar Radio Emission ◽  
Solar Cycles ◽  
Quiet Sun ◽  
Data Centre ◽  
National Geophysical Data ◽  
Using Data

AbstractRadio observations play a very important role in understanding the structure of the solar atmosphere. In this paper the quiet sun component of the solar radio emission has been investigated using data obtained from the Solar Indices Bulletin, National Geophysical Data Centre. By statistical method, the quiet sun component is estimated for 84 successive basic periods containing three solar rotations each using data obtained at different frequencies. From the quiet sun component we estimate the brightness temperature in each observing frequency.

Revisiting the Classical Experiment in Earthquake Control at the Rangely Oil Field, Colorado, 1970, Using a Coupled Flow and Geomechanical Model

2021 ◽  
Author(s):  
Josimar A. Silva ◽  
Hannah Byrne ◽  
Andreas Plesch ◽  
John H. Shaw ◽  
Ruben Juanes
Keyword(s):  
Pore Pressure ◽  
Oil Field ◽  
Coupled Flow ◽  
Injection Wells ◽  
Rock Types ◽  
Pressure Diffusion ◽  
Main Fault ◽  
Injection Interval ◽  
Using Data ◽  
Pressure Changes

ABSTRACT The injection experiment conducted at the Rangely oil field, Colorado, was a pioneering study that showed qualitatively the correlation between reservoir pressure increases and earthquake occurrence. Here, we revisit this field experiment using a mechanistic approach to investigate why and how the earthquakes occurred. Using data collected from decades of field operations, we build a geological model for the Rangely oil field, perform reservoir simulation to history match pore-pressure variations during the experiment, and perform geomechanical simulations to obtain stresses at the main fault, where the earthquakes were sourced. As a viable model, we hypothesize that pressure diffusion occurred through a system of highly permeable fractures, adjacent to the main fault in the field, connecting the injection wells to the area outside of the injection interval where intense seismic activity occurred. We also find that the main fault in the field is characterized by a friction coefficient μ  ≈  0.7—a value that is in good agreement with the classical laboratory estimates conducted by Byerlee for a variety of rock types. Finally, our modeling results suggest that earthquakes outside of the injection interval were released tectonic stresses and thus should be classified as triggered, whereas earthquakes inside the injection interval were driven mostly by anthropogenic pore-pressure changes and thus should be classified as induced.

Temporal variations of atmospheric ammonia (NH3) derived from over a decade of IASI satellite measurements

2021 ◽  
Author(s):  
Martin Van Damme ◽  
Lieven Clarisse ◽  
Bruno Franco ◽  
Mark A Sutton ◽  
Jan Willem Erisman ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
The Netherlands ◽  
Temporal Variation ◽  
Temporal Variations ◽  
Meteorological Conditions ◽  
Satellite Measurements ◽  
Atmospheric Sounding ◽  
National Trends ◽  
The Impact

<p>The Infrared Atmospheric Sounding Interferometer (IASI) mission consists of a suite of three infrared sounders providing today over 13 years of consistent global measurements (from end of 2007 up to now). In this work we use the recently developed version 3 of the IASI NH<sub>3</sub> dataset to derive global, regional and national trends from 2008 to 2018. Reported national trends are analysed in the light of changing anthropogenic and pyrogenic NH<sub>3</sub> emissions, meteorological conditions and the impact of sulphur and nitrogen oxides emissions. A case study is dedicated to the Netherlands. Temporal variation on shorter timescales will also be investigated.</p>

A STATISTICAL MODEL OF WINTER/SPRING POLAR OZONE

2021 ◽  
pp. 16-24
Author(s):  
N. S. Ivanova ◽  
Keyword(s):  
Statistical Analysis ◽  
Statistical Model ◽  
Zonal Wind ◽  
The Arctic ◽  
Satellite Measurements ◽  
Latitude Zone ◽  
Using Data ◽  
Polar Ozone

Satellite measurements provided by NASA (USA) at http://ozonewatch.gsfc.nasa.gov are used to study the variability and interdependence of polar ozone, polar temperature, and mean zonal wind. A model of winter/spring polar ozone in the Arctic and Antarctic is constructed using data on polar temperatures at 30, 70, and 100 hPa levels and mean zonal wind at 10 and 70 hPa levels in the latitude zone of 45°-75°. The results of the statistical analysis of the 1979-2020 polar ozone calculation errors are presented.

Sign in / Sign up

Export Citation Format

Share Document