Multi-decadal satellite measurements of global volcanic degassing

Carn, S. A.; Clarisse, Lieven; Prata, A. J.

doi:10.1016/j.jvolgeores.2016.01.002

Cited by 262 publications

(457 citation statements)

References 219 publications

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“…Space-based observations of this considerably weak source may be an option in the future but appear to be difficult with currently available instrumentation (e.g. Carn et al, 2016).…”

Section: Retrieved So 2 Emission Ratesmentioning

confidence: 99%

Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

et al. 2018

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Abstract. Accurate gas velocity measurements in emission plumes are highly desirable for various atmospheric remote sensing applications. The imaging technique of UV SO 2 cameras is commonly used to monitor SO 2 emissions from volcanoes and anthropogenic sources (e.g. power plants, ships). The camera systems capture the emission plumes at high spatial and temporal resolution. This allows the gas velocities in the plume to be retrieved directly from the images. The latter can be measured at a pixel level using optical flow (OF) algorithms. This is particularly advantageous under turbulent plume conditions. However, OF algorithms intrinsically rely on contrast in the images and often fail to detect motion in low-contrast image areas. We present a new method to identify ill-constrained OF motion vectors and replace them using the local average velocity vector. The latter is derived based on histograms of the retrieved OF motion fields. The new method is applied to two example data sets recorded at Mt Etna (Italy) and Guallatiri (Chile). We show that in many cases, the uncorrected OF yields significantly underestimated SO 2 emission rates. We further show that our proposed correction can account for this and that it significantly improves the reliability of optical-flow-based gas velocity retrievals.In the case of Mt Etna, the SO 2 emissions of the northeastern crater are investigated. The corrected SO 2 emission rates range between 4.8 and 10.7 kg s −1 (average of 7.1 ± 1.3 kg s −1 ) and are in good agreement with previously reported values. For the Guallatiri data, the emissions of the central crater and a fumarolic field are investigated. The retrieved SO 2 emission rates are between 0.5 and 2.9 kg s −1 (average of 1.3 ± 0.5 kg s −1 ) and provide the first report of SO 2 emissions from this remotely located and inaccessible volcano.

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“…Space-based observations of this considerably weak source may be an option in the future but appear to be difficult with currently available instrumentation (e.g. Carn et al, 2016).…”

Section: Retrieved So 2 Emission Ratesmentioning

confidence: 99%

Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

et al. 2018

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“…It thus has the potential to augment remote sensing observations in such applications as aerosol, cloud, sulfur dioxide and ozone amounts as well as vegetation properties . EPIC data are used for the remote sensing of clouds (Yang et al, 2013) and dust plumes with oxygen A and B bands (Xu et al, 2017); it also provides multispectral UV SO 2 measurements of the sunlit Earth disk (Carn et al, 2016). EPIC observations are also used to measure ozone, cloud reflectivity and erythemal irradiance (Herman et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Calibration of the DSCOVR EPIC visible and NIR channels using MODIS Terra and Aqua data and EPIC lunar observations

Geogdzhayev

Marshak

2018

Atmos. Meas. Tech.

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Abstract. The unique position of the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) at the Lagrange 1 point makes an important addition to the data from currently operating low Earth orbit observing instruments. EPIC instrument does not have an onboard calibration facility. One approach to its calibration is to compare EPIC observations to the measurements from polarorbiting radiometers. Moderate Resolution Imaging Spectroradiometer (MODIS) is a natural choice for such comparison due to its well-established calibration record and wide use in remote sensing. We use MODIS Aqua and Terra L1B 1 km reflectances to infer calibration coefficients for four EPIC visible and NIR channels: 443, 551, 680 and 780 nm. MODIS and EPIC measurements made between June 2015 and 2016 are employed for comparison. We first identify favorable MODIS pixels with scattering angle matching temporarily collocated EPIC observations. Each EPIC pixel is then spatially collocated to a subset of the favorable MODIS pixels within 25 km radius. Standard deviation of the selected MODIS pixels as well as of the adjacent EPIC pixels is used to find the most homogeneous scenes. These scenes are then used to determine calibration coefficients using a linear regression between EPIC counts s −1 and reflectances in the close MODIS spectral channels. We present thus inferred EPIC calibration coefficients and discuss sources of uncertainties. The lunar EPIC observations are used to calibrate EPIC O 2 absorbing channels (688 and 764 nm), assuming that there is a small difference between moon reflectances separated by ∼ 10 nm in wavelength and provided the calibration factors of the red (680 nm) and NIR (780 nm) are known from comparison between EPIC and MODIS.

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“…These have included the first instrumental networks of scanning Differential Optical Absorption Spectrometers (DOAS) for volcanic SO 2 flux monitoring, the implementation of satellite-based volcanic gas observations, and the advent of sensor units for in situ gas monitoring [1][2][3][4][5][6]. Owing to this technical progress, volcanic gas plume composition and fluxes have increasingly been used to extract information on degassing mechanisms/processes [4], and to derive constraints on shallow volcano plumbing systems [5].…”

Section: Introductionmentioning

confidence: 99%

“…In particular, it has been shown that, at open-vent persistently degassing volcanoes, volcanic eruptions are often preceded by anomalous increases of the volcanic CO 2 flux [7]. These initial observations have motivated attempts to systematically monitor the volcanic CO 2 flux, and to identify novel measurement strategies [8]. Until recently, however, attempts to remotely sense the volcanic CO 2 flux from distal locations have been limited in number [9,10], while the majority of the observations have involved in situ measurements in the proximity of hazardous active volcanic vents [3].…”

Section: Introductionmentioning

confidence: 99%

Volcanic Plume CO2 Flux Measurements at Mount Etna by Mobile Differential Absorption Lidar

et al. 2017

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Volcanic eruptions are often preceded by precursory increases in the volcanic carbon dioxide (CO 2 ) flux. Unfortunately, the traditional techniques used to measure volcanic CO 2 require near-vent, in situ plume measurements that are potentially hazardous for operators and expose instruments to extreme conditions. To overcome these limitations, the project BRIDGE (BRIDging the gap between Gas Emissions and geophysical observations at active volcanoes) received funding from the European Research Council, with the objective to develop a new generation of volcanic gas sensing instruments, including a novel DIAL-Lidar (Differential Absorption Light Detection and Ranging) for remote (e.g., distal) CO 2 observations. Here we report on the results of a field campaign carried out at Mt. Etna from 28 July 2016 to 1 August 2016, during which we used this novel DIAL-Lidar to retrieve spatially and temporally resolved profiles of excess CO 2 concentrations inside the volcanic plume. By vertically scanning the volcanic plume at different elevation angles and distances, an excess CO 2 concentration of tens of ppm (up to 30% above the atmospheric background of 400 ppm) was resolved from up to a 4 km distance from the plume itself. From this, the first remotely sensed volcanic CO 2 flux estimation from Etna's northeast crater was derived at ≈2850-3900 tons/day. This Lidar-based CO 2 flux is in fair agreement with that (≈2750 tons/day) obtained using conventional techniques requiring the in situ measurement of volcanic gas composition.

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Multi-decadal satellite measurements of global volcanic degassing

Cited by 262 publications

References 219 publications

Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

Calibration of the DSCOVR EPIC visible and NIR channels using MODIS Terra and Aqua data and EPIC lunar observations

Volcanic Plume CO2 Flux Measurements at Mount Etna by Mobile Differential Absorption Lidar

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Multi-decadal satellite measurements of global volcanic degassing

Cited by 262 publications

References 219 publications

Improved optical flow velocity analysis in SO&lt;sub&gt;2&lt;/sub&gt; camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

Improved optical flow velocity analysis in SO&lt;sub&gt;2&lt;/sub&gt; camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

Calibration of the DSCOVR EPIC visible and NIR channels using MODIS Terra and Aqua data and EPIC lunar observations

Volcanic Plume CO2 Flux Measurements at Mount Etna by Mobile Differential Absorption Lidar

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Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile

Improved optical flow velocity analysis in SO<sub>2</sub> camera images of volcanic plumes – implications for emission-rate retrievals investigated at Mt Etna, Italy and Guallatiri, Chile