The Experts below are selected from a list of 30837 Experts worldwide ranked by ideXlab platform
Frank Silvio Marzano - One of the best experts on this subject based on the ideXlab platform.
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Validating Subglacial Volcanic Eruption Using Ground-Based C-Band Radar Imagery
IEEE Transactions on Geoscience and Remote Sensing, 2012Co-Authors: Frank Silvio Marzano, Mirko Lamantea, Mario Montopoli, Björn Oddsson, Magnús Tumi GudmundssonAbstract:The main phase of the moderately sized November 2004 Eruption of the Grímsvötn volcano, located in the center of the 8100 km2 Vatnajökull glacier, was monitored by the Icelandic Meteorological Office C-band weather radar in Keflavík, 260 km west of the volcano. The Eruption plume reached a height of 6-10 km relative to the vent. The distribution of the most distal tephra was measured in the autumn of 2004, while the deposition on the glacier was mapped in the summers of 2005 and 2006. The tephra formed a well-defined layer on the glacier in the region north and northeast of the craters. The total mass of the tephra layer is quantitatively compared with the retrieved values, obtained from an improved version of the Volcanic ash radar retrieval (VARR) algorithm. VARR was statistically calibrated with ground-based ash size distribution samples, taken at Vatnajökull, and by taking into account both antenna beam occlusion and wind-driven plume advection. The latter was implemented by using a space-time image phase-based cross-correlation technique. Accuracy of the weather radar records was also reviewed, noting that a large variability in the plume height estimation may be obtained using different approaches. The comparisons suggest that, at least for this subglacial Eruption, the surface tephra mass, estimated by using the VARR inversion approach, is in a fairly good agreement with in situ measurements in terms of spatial extension, distribution, and amount.
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Monitoring Subglacial Volcanic Eruption Using Ground-Based C-Band Radar Imagery
IEEE Transactions on Geoscience and Remote Sensing, 2010Co-Authors: Frank Silvio Marzano, Stefano Barbieri, Errico Picciotti, SigrÙn KarlsdottirAbstract:The microphysical and dynamical features of Volcanic clouds, due to Plinian and sub-Plinian Eruptions, can be quantitatively monitored by using ground-based microwave weather radars. In order to demonstrate the unique potential of this remote sensing technique, a case study of a subglacial Volcanic Eruption, occurred in Iceland in November 2004, is described and analyzed. Volume data, acquired by a C-band ground-based weather radar, are processed to automatically classify and estimate ash particle concentration. The ash retrieval physical-statistical algorithm is based on a backscattering microphysical model of fine, coarse, and lapilli ash particles, used within a Bayesian classification and optimal regression algorithm. A sensitivity analysis is carried out to evaluate the overall error budget and the possible impact of nonprecipitating liquid and ice cloud droplets when mixed with ash particles. The evolution of the Icelandic Eruption is discussed in terms of radar measurements and products, pointing out the unique features, the current limitations, and future improvements of radar remote sensing of Volcanic plumes.
SigrÙn Karlsdottir - One of the best experts on this subject based on the ideXlab platform.
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Monitoring Subglacial Volcanic Eruption Using Ground-Based C-Band Radar Imagery
IEEE Transactions on Geoscience and Remote Sensing, 2010Co-Authors: Frank Silvio Marzano, Stefano Barbieri, Errico Picciotti, SigrÙn KarlsdottirAbstract:The microphysical and dynamical features of Volcanic clouds, due to Plinian and sub-Plinian Eruptions, can be quantitatively monitored by using ground-based microwave weather radars. In order to demonstrate the unique potential of this remote sensing technique, a case study of a subglacial Volcanic Eruption, occurred in Iceland in November 2004, is described and analyzed. Volume data, acquired by a C-band ground-based weather radar, are processed to automatically classify and estimate ash particle concentration. The ash retrieval physical-statistical algorithm is based on a backscattering microphysical model of fine, coarse, and lapilli ash particles, used within a Bayesian classification and optimal regression algorithm. A sensitivity analysis is carried out to evaluate the overall error budget and the possible impact of nonprecipitating liquid and ice cloud droplets when mixed with ash particles. The evolution of the Icelandic Eruption is discussed in terms of radar measurements and products, pointing out the unique features, the current limitations, and future improvements of radar remote sensing of Volcanic plumes.
Georgiy L Stenchikov - One of the best experts on this subject based on the ideXlab platform.
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impacts of a pinatubo size Volcanic Eruption on enso
Journal of Geophysical Research, 2017Co-Authors: Evgeniya Predybaylo, Georgiy L Stenchikov, Andrew T Wittenberg, Fanrong ZengAbstract:Observations and model simulations of the climate responses to strong explosive low-latitude Volcanic Eruptions suggest a significant increase in the likelihood of El Nino during the Eruption and post-Eruption years, though model results have been inconclusive and have varied in magnitude and even sign. In this study, we test how this spread of responses depends on the initial phase of El Nino-Southern Oscillation (ENSO) in the Eruption year, and on the Eruption's seasonal timing. We employ the GFDL CM2.1 global coupled general circulation model to investigate the impact of the Pinatubo 1991 Eruption, assuming that in 1991 ENSO would otherwise be in Central or Eastern Pacific El Nino, La Nina, or neutral phases. We obtain statistically significant El Nino responses in a year after the Eruption for all cases except La Nina, which shows no response in the eastern equatorial Pacific. The Eruption has a weaker impact on Eastern Pacific El Ninos than on Central Pacific El Ninos. We find that the ocean dynamical thermostat, and (to a lesser extent) wind changes due to land-ocean temperature gradients, are the main feedbacks affecting El Nino development after the Eruption. The El Nino responses to Eruptions occurring in summer are more pronounced than for winter and spring Eruptions. That the climate response depends on Eruption season and initial ENSO phase may help to reconcile apparent inconsistencies among previous studies.
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did the toba Volcanic Eruption of 74 ka b p produce widespread glaciation
Journal of Geophysical Research, 2009Co-Authors: Alan Robock, Caspar M Ammann, Luke D Oman, Drew T Shindell, Samuel Levis, Georgiy L StenchikovAbstract:[1] It has been suggested that the Toba Volcanic Eruption, approximately 74 ka B.P., was responsible for the extended cooling period and ice sheet advance immediately following it, but previous climate model simulations, using 100 times the amount of aerosols produced by the 1991 Mount Pinatubo Eruption, have been unable to produce such a prolonged climate response. Here we conduct six additional climate model simulations with two different climate models, the National Center for Atmospheric Research Community Climate System Model 3.0 (CCSM3.0) and National Aeronautics and Space Administration Goddard Institute for Space Studies ModelE, in two different versions, to investigate additional mechanisms that may have enhanced and extended the forcing and response from such a large superVolcanic Eruption. With CCSM3.0 we include a dynamic vegetation model to explicitly calculate the feedback of vegetation death on surface fluxes in response to the large initial reduction in transmitted light, precipitation, and temperature. With ModelE we explicitly calculate the effects of an Eruption on stratospheric water vapor and model stratospheric chemistry feedbacks that might delay the conversion of SO 2 into sulfate aerosols and prolong the lifetime and radiative forcing of the stratospheric aerosol cloud. To span the uncertainty in the amount of stratospheric injection of SO 2 , with CCSM3.0 we used 100 times the Pinatubo injection, and with ModelE we used 33, 100, 300, and 900 times the Pinatubo injection without interactive chemistry, and 300 times Pinatubo with interactive chemistry. Starting from a roughly present-day seasonal cycle of insolation, CO 2 concentration, and vegetation, or with 6 ka B.P. conditions for CCSM3.0, none of the runs initiates glaciation. The CCSM3.0 run produced a maximum global cooling of 10 K and ModelE runs produced 8-17 K of cooling within the first years of the simulation, depending on the injection, but in all cases, the climate recovers over a few decades. Nevertheless, the "Volcanic winter" following a supervolcano Eruption of the size of Toba today would have devastating consequences for humanity and global ecosystems. These simulations support the theory that the Toba Eruption indeed may have contributed to a genetic bottleneck.
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radiative forcing from the 1991 mount pinatubo Volcanic Eruption
Journal of Geophysical Research, 1998Co-Authors: Georgiy L Stenchikov, Alan Robock, Ingo Kirchner, Hansf Graf, Juan Carlos Antuna, R G Grainger, A Lambert, L W ThomasonAbstract:Volcanic sulfate aerosols in the stratosphere produce significant long-term solar and infrared radiative perturbations in the Earth's atmosphere and at the surface, which cause a response of the climate system. Here we study the fundamental process of the development of this Volcanic radiative forcing, focusing on the Eruption of Mount Pinatubo in the Philippines on June 15, 1991. We develop a spectral-, space-, and time-dependent set of aerosol parameters for 2 years after the Pinatubo Eruption using a combination of SAGE II aerosol extinctions and UARS-retrieved effective radii, supported by SAM II, AVHRR, lidar and balloon observations. Using these data, we calculate the aerosol radiative forcing with the ECHAM4 general circulation model (GCM) for cases with climatological and observed sea surface temperature (SST), as well as with and without climate response. We find that the aerosol radiative forcing is not sensitive to the climate variations caused by SST or the atmospheric response to the aerosols, except in regions with varying dense cloudiness. The solar forcing in the near infrared contributes substantially to the total stratospheric heating. A complete formulation of radiative forcing should include not only changes of net fluxes at the tropopause but also the vertical distribution of atmospheric heating rates and the change of downward thermal and net solar radiative fluxes at the surface. These forcing and aerosol data are available for GCM experiments with any spatial and spectral resolution.
Tamsin A Mather - One of the best experts on this subject based on the ideXlab platform.
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the influence of great earthquakes on Volcanic Eruption rate along the chilean subduction zone
Earth and Planetary Science Letters, 2009Co-Authors: Sebastian F L Watt, David M Pyle, Tamsin A MatherAbstract:Seismic activity has been postulated as a trigger of Volcanic Eruption on a range of timescales, but demonstrating the occurrence of triggered Eruptions on timescales beyond a few days has proven difficult using global datasets. Here, we use the historic earthquake and Eruption records of Chile and the Andean southern Volcanic zone to investigate Eruption rates following large earthquakes. We show a significant increase in Eruption rate following earthquakes of MW > 8, notably in 1906 and 1960, with similar occurrences further back in the record. Eruption rates are enhanced above background levels for ~ 12 months following the 1906 and 1960 earthquakes, with the onset of 3–4 Eruptions estimated to have been seismically influenced in each instance. Eruption locations suggest that these effects occur from the near-field to distances of ~ 500 km or more beyond the limits of the earthquake rupture zone. This suggests that both dynamic and static stresses associated with large earthquakes are important in Eruption-triggering processes and have the potential to initiate Volcanic Eruption in arc settings over timescales of several months.
Magnús Tumi Gudmundsson - One of the best experts on this subject based on the ideXlab platform.
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Validating Subglacial Volcanic Eruption Using Ground-Based C-Band Radar Imagery
IEEE Transactions on Geoscience and Remote Sensing, 2012Co-Authors: Frank Silvio Marzano, Mirko Lamantea, Mario Montopoli, Björn Oddsson, Magnús Tumi GudmundssonAbstract:The main phase of the moderately sized November 2004 Eruption of the Grímsvötn volcano, located in the center of the 8100 km2 Vatnajökull glacier, was monitored by the Icelandic Meteorological Office C-band weather radar in Keflavík, 260 km west of the volcano. The Eruption plume reached a height of 6-10 km relative to the vent. The distribution of the most distal tephra was measured in the autumn of 2004, while the deposition on the glacier was mapped in the summers of 2005 and 2006. The tephra formed a well-defined layer on the glacier in the region north and northeast of the craters. The total mass of the tephra layer is quantitatively compared with the retrieved values, obtained from an improved version of the Volcanic ash radar retrieval (VARR) algorithm. VARR was statistically calibrated with ground-based ash size distribution samples, taken at Vatnajökull, and by taking into account both antenna beam occlusion and wind-driven plume advection. The latter was implemented by using a space-time image phase-based cross-correlation technique. Accuracy of the weather radar records was also reviewed, noting that a large variability in the plume height estimation may be obtained using different approaches. The comparisons suggest that, at least for this subglacial Eruption, the surface tephra mass, estimated by using the VARR inversion approach, is in a fairly good agreement with in situ measurements in terms of spatial extension, distribution, and amount.
