The HOTSAT volcano monitoring system based on combined use of SEVIRI and MODIS multispectral data

Spaceborne remote sensing of high-temperature volcanic features offers an excellent opportunity to monitor the onset and development of new eruptive activity. To provide a basis for real-time response during eruptive events, we designed and developed the volcano monitoring system that we call HOTSAT. This multiplatform system can elaborate both Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data, and it is here applied to the monitoring of the Etna volcano. The main advantage of this approach is that the different features of both of these sensors can be used. It can be refreshed every 15 min due to the high frequency of the SEVIRI acquisition, and it can detect smaller and/or less intense thermal anomalies through the MODIS data. The system consists of data preprocessing, detection of volcano hotspots, and radiative power estimation. To locate thermal anomalies, a new contextual algorithm is introduced that takes advantage of both the spectral and spatial comparison methods. The derivation of the radiative power is carried out at all ‘hot’ pixels using the middle infrared radiance technique. The whole processing chain was tested during the 2008 Etna eruption. The results show the robustness of the system after it detected the lava fountain that occurred on May 10 through the SEVIRI data, and the very beginning of the eruption on May 13 through the MODIS data analysis

Early Analysis of Landsat-8 Thermal Infrared Sensor Imagery of Volcanic Activity

The Landsat-8 satellite of the Landsat Data Continuity Mission was launched by the National Aeronautics and Space Administration (NASA) in April 2013. Just weeks after it entered active service, its sensors observed activity at Paluweh Volcano, Indonesia. Given that the image acquired was in the daytime, its shortwave infrared observations were contaminated with reflected solar radiation; however, those of the satellite’s Thermal Infrared Sensor (TIRS) show thermal emission from the volcano’s summit and flanks. These emissions detected in sensor’s band 10 (10.60–11.19 µm) have here been quantified in terms of radiant power, to confirm reports of the actual volcanic processes operating at the time of image acquisition, and to form an initial assessment of the TIRS in its volcanic observation capabilities. Data from band 11 have been neglected as its data have been shown to be unreliable at the time of writing. At the instant of image acquisition, the thermal emission of the volcano was found to be 345 MW. This value is shown to be on the same order of magnitude as similarly timed NASA Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer thermal observations. Given its unique characteristics, the TIRS shows much potential for providing useful, detailed and accurate volcanic observations in the future

Role of Emissivity in Lava Flow ‘Distance-to-Run’ Estimates from Satellite-Based Volcano Monitoring

Remote sensing is an established technological solution for bridging critical gaps in volcanic hazard assessment and risk mitigation. The enormous amount of remote sensing data available today at a range of temporal and spatial resolutions can aid emergency management in volcanic crises by detecting and measuring high-temperature thermal anomalies and providing lava flow propagation forecasts. In such thermal estimates, an important role is played by emissivity—the efficiency with which a surface radiates its thermal energy at various wavelengths. Emissivity has a close relationship with land surface temperatures and radiant fluxes, and it impacts directly on the prediction of lava flow behavior, as mass flux estimates depend on measured radiant fluxes. Since emissivity is seldom measured and mostly assumed, we aimed to fill this gap in knowledge by carrying out a multi-stage experiment, combining laboratory-based Fourier transform infrared (FTIR) analyses, remote sensing data, and numerical modeling. We tested the capacity for reproducing emissivity from spaceborne observations using ASTER Global Emissivity Database (GED) while assessing the spatial heterogeneity of emissivity. Our laboratory-satellite emissivity values were used to establish a realistic land surface temperature from a high-resolution spaceborne payload (ETM+) to obtain an instant temperature⁻radiant flux and eruption rate results for the 2001 Mount Etna (Italy) eruption. Forward-modeling tests conducted on the 2001 ‘aa’ lava flow by means of the MAGFLOW Cellular Automata code produced differences of up to ~600 m in the simulated lava flow ‘distance-to-run’ for a range of emissivity values. Given the density and proximity of urban settlements on and around Mount Etna, these results may have significant implications for civil protection and urban planning applications

Radiant and mass fluxes in multi-platform, multi-payload satellite-based volcano monitoring

The enormous amount of remote sensing (RS) data available today at a range of temporal and spatial resolutions aid emergency management in volcanic crises. RS provides a technological solution for bridging critical gaps in volcanic hazard assessment and risk mitigation. Detection and measurement of high-temperature thermal anomalies enable eruption monitoring and new lava flow propagation forecasts, for example. The accuracy of such thermal estimates relies on the knowledge of input parameters, such as emissivity - the efficiency with which surfaces radiate thermal energy at various wavelengths and temperatures. Emissivity is directly linked to the measurement of radiant flux and therefore affects the mass flux estimate as well as any model-based prediction of lava flow behaviour. Emissivity is not commonly measured across the range of volcanic lava compositions and temperatures, and it is generally assumed to have a constant value between 1.0 and 0.80 for basaltic lava. There is a lack of field and laboratory-based emissivity data for robust, more realistic modelling. To address this deficit, experiments on ‘aa’ lava samples were performed using data from Mount Etna (Italy), representing the range of its eruptive behaviour. In three sequential stages, emissivity was measured over the widest range of temperatures (294 – 1373 K) and wavelengths (2.17 - 15.0 μm) executable in the laboratory environment.The results show that emissivity is temperature, composition and wavelength dependent. Measured emissivity increases non-linearly with temperature decrease (cooling), exhibiting significant variations above 900 K with values considerably lower than the typically assumed 0.80. The measured and modelled emissivity values were applied to various remote sensing applications as input parameters for physical modelling of lava flows. This new evidence has significant impact on the computation of radiant heat flux from spaceborne data, as well as on modelling of lava flow ‘distance-to-run’ simulations. Furnished with improved input parameters (multicomponent emissivity), the novel approach developed here can be used to test an improved version of an unsupervised multi-platform, multi-payload volcano monitoring system

SEVIRI onboard Meteosat Second Generation, and the quantitative monitoring of effusive volcanoes in Europe and Africa

The spectral and radiometric performance of payload SEVIRI onboard the geostationary platform MSG-2, make its data particularly well suited not only to the detection of the onset of volcanic activity, but also to the measurement of thermal radiant fluxes and eruption rates. Thorough testing was carried out on two volcanoes - Stromboli (Aeolian Islands, Southern Italy) and Piton de la Fournaise (Réunion Island, northwestern Indian Ocean) - that mostly give rise to short-lived lava flows. Aimed to comply with the outstandingly high acquisition rate, we developed an ad-hoc code to automatically detect volcanic hot-spots, measure radiant fluxes, and derive lava volume effusion rates within the 15-minute interval between two SEVIRI data streams. © 2008 IEEE