scholarly journals GPS tomography tests for DInSAR applications on Mt. Etna

2015 ◽  
Vol 58 (3) ◽  
Author(s):  
Massimo Aranzulla ◽  
Giuseppe Puglisi
Keyword(s):  
Electromagnetic Waves ◽  
A Priori ◽  
Geodetic Network ◽  
Atmospheric Model ◽  
Volcanic Area ◽  
Random Choice ◽  
Gps Receivers ◽  
Tomographic Images ◽  
Mt Etna ◽  
Radar Wave

<p>Tropospheric artifacts of SAR images in a volcanic area like Mt. Etna cause ambiguity in the interpretation of deformations with such technique. It would be useful to measure the delay caused by tropospheric anomalies in synthetic aperture radar (SAR) satellite signals (phase of the back-scattered radar wave) that could be interpreted as deformation. From the delay estimated through the GPS data processing, the tropospheric tomography of electromagnetic waves refractivity, has been performed using the SIMULps12 software. The aim of this study was to perform software synthetic tests by using SIMULps12 applied to atmospheric tomography and to verify the influence of the different GPS geodetic network configurations on obtaining a reliable tomography. Three different anomalies of increasing complexity have been investigated in order to understand the representative parameters of a correct tomography, the best spatial resolution and the portions of space in which the tomography is reliable. The tests also focused on fixing/establishing the a-priori atmospheric model and the critical values of the main parameters involved in the tomographic inversion. To this end, we made a random choice of two days, necessary to define the tomographic problem. Three different network configurations with 15, 30 and 90 GPS receivers were studied. The results indicate that the well-resolved area of tomographic images increases with the number of GPS receivers not linearly, and that the actual GPS network of 42 receivers is capable of revealing/detecting the atmospheric anomalies.</p>

scholarly journals Real time retrieval of volcanic cloud particles and SO<sub>2</sub> by satellite using an improved simplified approach

2016 ◽  
Vol 9 (7) ◽  
pp. 3053-3062 ◽  
Author(s):  
Sergio Pugnaghi ◽  
Lorenzo Guerrieri ◽  
Stefano Corradini ◽  
Luca Merucci
Keyword(s):  
Sulfur Dioxide ◽  
Atmospheric Model ◽  
Volcanic Plume ◽  
Volcanic Area ◽  
Simplified Approach ◽  
Mt Etna ◽  
Plume Temperature ◽  
Volcanic Cloud ◽  
Preliminary Preparation ◽  
The Mean

Abstract. Volcanic plume removal (VPR) is a procedure developed to retrieve the ash optical depth, effective radius and mass, and sulfur dioxide mass contained in a volcanic cloud from the thermal radiance at 8.7, 11, and 12 µm. It is based on an estimation of a virtual image representing what the sensor would have seen in a multispectral thermal image if the volcanic cloud were not present. Ash and sulfur dioxide were retrieved by the first version of the VPR using a very simple atmospheric model that ignored the layer above the volcanic cloud. This new version takes into account the layer of atmosphere above the cloud as well as thermal radiance scattering along the line of sight of the sensor. In addition to improved results, the new version also offers an easier and faster preliminary preparation and includes other types of volcanic particles (andesite, obsidian, pumice, ice crystals, and water droplets). As in the previous version, a set of parameters regarding the volcanic area, particle types, and sensor is required to run the procedure. However, in the new version, only the mean plume temperature is required as input data. In this work, a set of parameters to compute the volcanic cloud transmittance in the three quoted bands, for all the aforementioned particles, for both Mt. Etna (Italy) and Eyjafjallajökull (Iceland) volcanoes, and for the Terra and Aqua MODIS instruments is presented. Three types of tests are carried out to verify the results of the improved VPR. The first uses all the radiative transfer simulations performed to estimate the above mentioned parameters. The second one makes use of two synthetic images, one for Mt. Etna and one for Eyjafjallajökull volcanoes. The third one compares VPR and Look-Up Table (LUT) retrievals analyzing the true image of Eyjafjallajökull volcano acquired by MODIS aboard the Aqua satellite on 11 May 2010 at 14:05 GMT.

scholarly journals Real time retrieval of volcanic cloud particles and SO<sub>2</sub> by satellite using an improved simplified approach

2016 ◽  
Author(s):  
S. Pugnaghi ◽  
L. Guerrieri ◽  
S. Corradini ◽  
L. Merucci
Keyword(s):  
Sulphur Dioxide ◽  
Atmospheric Model ◽  
Volcanic Plume ◽  
Volcanic Area ◽  
Simplified Approach ◽  
Mt Etna ◽  
Plume Temperature ◽  
Volcanic Cloud ◽  
Preliminary Preparation ◽  
Ice Water

Abstract. Volcanic Plume Removal (VPR) is a procedure developed to retrieve the ash optical depth, effective radius and mass, and sulphur dioxide mass contained in a tropospheric volcanic cloud from the thermal radiance at 8.7, 11, and 12 μm. It is based on an estimation of a virtual image representing what the sensor would have seen in a multispectral thermal image if the volcanic cloud were not present. Ash and sulphur dioxide were retrieved by the first version of the VPR using a very simple atmospheric model that ignored the layer above the volcanic cloud. This new version takes into account the layer of atmosphere above the cloud as well as thermal radiance scattering along the line of sight of the sensor. In addition to improved results, the new version also offers easier and faster preliminary preparation and includes other types of volcanic particles. As in the previous version, a set of parameters regarding the volcanic area, particle types, and sensor are required to run the procedure. However, in the new version, only the mean plume temperature is required as input data. It this work a set of parameters have been computed for different types of plume particles (andesite, obsidian, pumice, ice, water, and sulphuric acid droplets), for both the Mt. Etna (Italy) and Eyjafjallajökull (Iceland) volcanoes, and for the MODIS Terra and Aqua instruments. Two different synthetic images, one for Mt. Etna and one for Eyjafjallajökull, are used to compare the results from the new and old procedures. Finally, a sensitivity analysis was conducted to investigate variations in VPR ash and sulphur dioxide retrievals as a function of plume altitude and particle type.

scholarly journals Application of the Wiener filter to magnetic profiling in the volcanic environment of Mt. Etna (Italy)

1996 ◽  
Vol 39 (1) ◽  
Author(s):  
C. Del Negro
Keyword(s):  
Synthetic Data ◽  
Wiener Filter ◽  
Magnetic Anomalies ◽  
Fault System ◽  
Volcanic Area ◽  
Wiener Filters ◽  
Mt Etna ◽  
Band Pass ◽  
Magnetic Profile ◽  
Mean Square Error Criterion

The frequency-domain Wiener filtering was applied to magnetic anomalies in the volcanic area of Mt. Etna. This filter, under suitable conditions (additive noise, linear processing and mean-square error criterion), can furnish an effective tool for discriminating the geologic feature of interest (the signal) from the noise. The filter was first tested with synthetic data. Afterwards it was applied to a magnetic profile carried out across the principal fault system of the Mt. Etna volcano, that hosted the dykes feeding both the 1989 and the 1991-93 eruptions. The magnetic anomalies linked to the volcanic section and those linked to the contact between the clay basement and the lava coverage show significant spectral overlap. Thus by estimating the power spectrum of the signal, obtained resolving the forward problem, a least-squares Wiener filter has been designed. In such context, it was possible to verify the effectiveness of Wiener filters, whereas traditional band-pass filtering proved inadequate. In fact, analysis of the noise showed that all the meaningful components of the observed magnetic field were resolved. The results put further constraints on location and geometry of the shallow plumbing system of Mt. Etna.

scholarly journals Atmospheric bending effects in GNSS tomography

2019 ◽  
Vol 12 (1) ◽  
pp. 23-34 ◽  
Author(s):  
Gregor Möller ◽  
Daniel Landskron
Keyword(s):  
Ray Tracing ◽  
Electromagnetic Waves ◽  
Piecewise Linear ◽  
A Priori ◽  
Elevation Angle ◽  
Functional Relation ◽  
Satellite System ◽  
Neutral Atmosphere ◽  
Correct Treatment ◽  
Reconstructed Signal

Abstract. In Global Navigation Satellite System (GNSS) tomography, precise information about the tropospheric water vapor distribution is derived from integral measurements like ground-based GNSS slant wet delays (SWDs). Therefore, the functional relation between observations and unknowns, i.e., the signal paths through the atmosphere, have to be accurately known for each station–satellite pair involved. For GNSS signals observed above a 15∘ elevation angle, the signal path is well approximated by a straight line. However, since electromagnetic waves are prone to atmospheric bending effects, this assumption is not sufficient anymore for lower elevation angles. Thus, in the following, a mixed 2-D piecewise linear ray-tracing approach is introduced and possible error sources in the reconstruction of the bended signal paths are analyzed in more detail. Especially if low elevation observations are considered, unmodeled bending effects can introduce a systematic error of up to 10–20 ppm, on average 1–2 ppm, into the tomography solution. Thereby, not only the ray-tracing method but also the quality of the a priori field can have a significant impact on the reconstructed signal paths, if not reduced by iterative processing. In order to keep the processing time within acceptable limits, a bending model is applied for the upper part of the neutral atmosphere. It helps to reduce the number of processing steps by up to 85 % without significant degradation in accuracy. Therefore, the developed mixed ray-tracing approach allows not only for the correct treatment of low elevation observations but is also fast and applicable for near-real-time applications.

Estimates of anthropogenic CO2 emissions from satellite and ground based measurements

2020 ◽  
Author(s):  
Yury Timofeyev ◽  
George Nerobelov ◽  
Sergey Smyshlyaev ◽  
Ivan Berezin ◽  
Yana Virolainen ◽  
...  
Keyword(s):  
Measurement Errors ◽  
Numerical Models ◽  
Dispersion Model ◽  
A Priori ◽  
Three Dimensional ◽  
Atmospheric Model ◽  
Experimental Information ◽  
Anthropogenic Emissions ◽  
Plume Dispersion ◽  
Satellite Measurements

&lt;p&gt;In recent years, satellite methods have played an important role in CO&lt;sub&gt;2&lt;/sub&gt; monitoring. Various satellite instruments (SCIAMACHY, AIRS, GOSAT, OCO-2, etc.) validated by ground-based and aircraft measurements allow to retrieving the column averaged CO&lt;sub&gt;2&lt;/sub&gt; mixing ratio (X&lt;sub&gt;CO2&lt;/sub&gt;) with high accuracy (0.25&amp;#8211;1.0%). The relatively high spatial resolution of a number of instruments (for example, OCO-2) allows studies of spatial and temporal CO&lt;sub&gt;2&lt;/sub&gt; variations, that, under appropriate conditions, makes it possible to estimate anthropogenic emissions from different cities.&lt;/p&gt;&lt;p&gt;Various techniques (source pixel mass balance method, plume dispersion model and atmospheric inversion system) for determining anthropogenic greenhouse gas emissions from data of satellite measurements are considered.&lt;/p&gt;&lt;p&gt;On the basis of three-dimensional modeling and comparison with the results of various local and remote measurements, numerical models of the atmosphere were adapted to different megacities of Russia. Based on numerical experiments, the errors of various satellite techniques for determining emissions caused by various factors (measurement errors, quality of used a priori and additional experimental information, adequacy of used numerical atmospheric model, etc.) were evaluated. Anthropogenic CO&lt;sub&gt;2&lt;/sub&gt; emissions in St. Petersburg, Moscow and other cities of Russia are estimated using various satellite measurements. These estimates of anthropogenic emissions are compared with data obtained by different methods and for different cities.&lt;/p&gt;

Intrusive mechanism of the 2008–2009 Mt. Etna eruption: Constraints by tomographic images and stress tensor analysis

2012 ◽  
Vol 229-230 ◽  
pp. 50-63 ◽  
Author(s):  
Salvatore Alparone ◽  
Graziella Barberi ◽  
Ornella Cocina ◽  
Elisabetta Giampiccolo ◽  
Carla Musumeci ◽  
...  
Keyword(s):  
Stress Tensor ◽  
Tensor Analysis ◽  
Tomographic Images ◽  
Mt Etna

scholarly journals Comparison of the SST-Forced Responses between Coupled and Uncoupled Climate Simulations

2014 ◽  
Vol 27 (2) ◽  
pp. 740-756 ◽  
Author(s):  
Hua Chen ◽  
Edwin K. Schneider
Keyword(s):  
A Priori ◽  
Atmospheric Model ◽  
Forced Response ◽  
Climate Simulations ◽  
Perfect Model ◽  
Time Lagged ◽  
Forced Responses ◽  
The Tropics ◽  
Indirect Tests ◽  
Linear Regressions

Abstract It is commonly assumed that a reasonable estimate of the SST-forced component of the observed atmospheric circulation is given by an atmospheric GCM (AGCM) forced with the observed SST. However, there are results that find different SST-forced responses from the observed, for example for the ENSO–monsoon relationship, and suggest that these differences are due to lack of coupling to the ocean rather than atmospheric model bias unrelated to coupling. Here, the coupling issue is isolated and examined through perfect model experiments. A coupled atmosphere–ocean GCM (CGCM) simulation and an AGCM simulation forced by the SST from the CGCM are compared to examine whether the SST-forced responses are the same. This question cannot be addressed directly, since the SST-forced response of the CGCM is a priori unknown. Therefore, two indirect tests are applied, based on the assumption that the noise decorrelation time scale is short compared to a month. The first test is to compare the time-lagged linear regressions of the atmospheric fields onto several SST indices (defined as the area-averaged SST anomalies in the tropics or extratropics), with SST leading the atmosphere by a month. The second test is to compare the time lagged linear covariances of several atmospheric indices (including two monsoon indices and a North Atlantic Oscillation index) and SST, with the SST leading the atmosphere by a month. Both tests find that the SST-forced responses are the same in the CGCM and SST-forced AGCM. These tests can be extended to compare the SST-forced responses between different AGCMs, CGCMs, and observations.

scholarly journals The role of electrical conductivity in radarwave reflection

2020 ◽  
Author(s):  
Slawek M. Tulaczyk ◽  
Neil T. Foley
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Specular Reflection ◽  
A Priori ◽  
Normal Incidence ◽  
Radar Reflectivity ◽  
Geologic Materials ◽  
Wide Range ◽  
Radar Wave ◽  
The Impact

Abstract. We have examined a general expression giving the specular reflection coefficient for a radar wave approaching a reflecting interface with normal incidence. The reflecting interface separates two homogeneous media, the properties of which are fully described by three scalar quantities: dielectric permittivity, magnetic permeability, and electrical conductivity. The derived relationship indicates that electrical conductivity should not be neglected a priori in glaciological investigations of subglacial materials, and in GPR studies of saturated sediments and bedrock, even at the high end of typical linear radar frequencies used in such investigations (e.g., 100 MHz). Our own experience in resistivity surveying in Antarctica, combined with a literature review, suggests that a wide range of geologic materials can have electrical conductivity that is high enough to significantly impact the value of radar reflectivity. Furthermore, we have given two examples of prior studies in which inclusion of electrical conductivity in calculation of the radar bed reflectivity may provide an explanation for results that may be considered surprising if the impact of electrical conductivity on radar reflection is neglected. The commonly made assumption that only dielectric permittivity of the two media need to be considered in interpretation of radar reflectivity can lead to erroneous conclusions.

Mercury in the environment of the Mt. Etna volcanic area

1988 ◽  
Vol 9 (3) ◽  
pp. 239-244 ◽  
Author(s):  
C. Barghigiani ◽  
R. Bargagli ◽  
D. Gioffré
Keyword(s):  
Volcanic Area ◽  
Mt Etna

scholarly journals Tomographic images and 3D earthquake locations of the seismic swarm preceding the 2001 Mt. Etna eruption: Evidence for a dyke intrusion

2002 ◽  
Vol 29 (10) ◽  
pp. 135-1-135-4 ◽  
Author(s):  
Domenico Patane ◽  
Claudio Chiarabba ◽  
Ornella Cocina ◽  
Pasquale De Gori ◽  
Milena Moretti ◽  
...  
Keyword(s):  
Tomographic Images ◽  
Earthquake Locations ◽  
Seismic Swarm ◽  
Dyke Intrusion ◽  
Mt Etna
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