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

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

Near Real-Time Monitoring of the Christmas 2018 Etna Eruption Using SEVIRI and Products Validation

“…For the distal monitoring, VCTH is computed by applying the same procedure described for the VPTH parameter but considering the whole volcanic cloud, while the ash and SO 2 detection and retrievals are obtained by exploiting the SEVIRI channels centred at 8.7, 10.8, and 12 µm (SEVIRI channels 7, 9, and 10, respectively). The detection is realized through a Red Green Blue (RGB) composite obtained by combining the brightness temperatures (T b ) of the three SEVIRI channels (R: T b,8.7 -T b,10.8 ; G: T b,12 -T b,10.8 ; B: T b,10.8 ), while the quantitative estimation of the different ash and SO 2 parameters are computed by exploiting the Volcanic Plume Retrieval (VPR) procedure, formerly Volcanic Plume Removal [16][17][18]50]. VPR requires in input only the VCTH and is based on the computation of a new image by replacing the radiance values in the region occupied by the plume with those obtained from a simple linear regression of the radiance outside the edges of the plume itself.…”

Characterization of Volcanic Cloud Components Using Machine Learning Techniques and SEVIRI Infrared Images

“…The SVM technique was already applied to volcano monitoring, and it was demonstrated that it provides successful results [ 71 , 72 ], due to its high performance and lower computation costs. Until now, algorithms and models have been developed for the retrieval of the components of a volcanic cloud [ 73 , 74 , 75 ] but without the implementation of artificial intelligence approaches. However, machine learning and deep learning techniques have been exploited mainly for the detection of a volcanic cloud [ 63 , 66 , 76 , 77 ].…”

Examples of Multi-Sensor Determination of Eruptive Source Parameters of Explosive Events at Mount Etna

“…Quantitative ESPs from SEVIRI data are derived using the volcanic plume retrieval algorithm to estimate the amount of fine ash and also SO 2 carried by volcanic clouds (VPR; [7,29,[54][55][56]). This procedure allows removing the detected volcanic cloud from satellite images by a linear interpolation of the radiances at the plume edges.…”