A new simplified procedure for the simultaneous SO<sub>2</sub> and ash retrieval in a tropospheric volcanic cloud

Abstract. A new procedure for the simultaneous estimation of SO2 and ash abundances in a volcanic plume using thermal infrared (TIR) MODIS data is presented. Plume altitude and temperature are the only two input parameters needed to run the procedure, while surface emissivity, atmospheric profiles and radiative transfer models are not required to perform the atmospheric corrections. The proposed space-based retrievals are simple, extremely fast and can be easily extended and applied to any volcano. By linearly interpolating the radiances of the edges of the detected volcanic plume, the Volcanic Plume Removal (VPR) procedure here described, computes the radiances that would have been measured at the sensor if the plume was missing and reconstructs a new image without the plume. The comparison of the new image with the original data containing the plume highlights the plume presence and allows the computation of the plume transmittance in three TIR-MODIS bands: 29, 31 and 32 (8.6, 11.0 and 12.0 μm). The procedure results are very good when the surface under the plume is rather uniform, as it is often the case with plume widths of few tens of kilometers. As a consequence it works very well when the plume is above the sea, but still produces fairly good estimates in more challenging and not easily modeled conditions, such as images with land or uniform cloud layers under the plume. In the aforementioned bands the plume transmittances are derived in two steps: (1) using a simple model with the plume at a fixed altitude and neglecting the layer of atmosphere above it; (2) refining the first result with a polynomial relationship obtained by means of MODTRAN simulations adapted for the geographical region, the ash type and the atmospheric profiles. Bands 31 and 32 are SO2 transparent and, from their transmittances, the ash particle effective radius (Re) and the aerosol optical depth at 550 nm (AOD550) are computed. A simple relation between the ash transmittances of bands 31 and 29 is demonstrated and used for the SO2 columnar content estimation. Comparing the results of the VPR procedure with the MODTRAN simulations for more than 200 thousands different cases, the frequency distribution of the differences says that: the Re error is less than ±0.5 μm in more than the 60% of the cases; the AOD550 error is less than ±0.125 in the 80% of the cases; the SO2 error is less than ±0.5 g m−2 in more than the 60% of the considered cases. The VPR procedure has been applied in two case studies of recent eruptions occurred at Mt. Etna volcano, Italy and successfully compared with the results obtained with the well known SO2 and ash retrievals based look-up tables (LUTs). By recomputing the parameters of the polynomial relationship, the VPR procedure can be easily extended to other ash types and applied to different volcanoes. </jats:p

Flexible Energy Supply for Distributed Electronics Powered by Organic Solar Cell and Printed Supercapacitor

In this work we report a flexible energy supply unit made by printing flexible disposable aqueous supercapacitor modules onto a light harvester. In order to demonstrate simpler and more scalable manufacturing processes, we printed the supercapacitors monolithically instead of laminating electrodes face-to-face and integrated the series connections into the fabrication process. The supercapacitor modules were printed onto the backside of the Organic Photovoltaic (OPV) modules to combine energy harvesting and storage module for harvesting light under normal indoor conditions, storing it in a supercapacitor module, and thus offering power for low power IoT devices.acceptedVersionPeer reviewe