The availability of EO satellites in the last decades has offered the possibility to integrate the ground surveillance with
satellite derived information increasing the knowledge of territory situation and phenomena characteristics during natural
disasters. All member states of the European Union are affected by at least one major natural hazard such as Floods,
Fires, Windstorms, Earthquakes, Volcanoes, Landslides, Rapid vertical ground displacements, and also by risks related
to man-made activities such as chemical and nuclear accidents. The above mentioned risks can be mitigated through a
better prevention and preparedness within a multi-risk joint effort of all actors in risk management and integration of
societal needs.
In this frame the EC FP6 Preview-Eurorisk project aims at developing new geo-information services for atmospheric,
geophysical and man-made risk management at a European level; the End-Users of these services are represented by the
Civil Defence Agencies of the different partner countries.
In the Geophysical Cluster dedicated to earthquakes and volcanoes risks, a prototype system to support end-users (i.e.
national Civil Protections) has been developed. The service separates the natural phenomena in 3 main phases: earlywarning,
crisis management and post-crisis.
The service prototype provides easy and rapid access to assets mapping, mapping, monitoring, forecasting and awareness
of risk as well as damage assessment at European, regional and local levels according to the operative necessities of the
End-Users.
The system products chain consists in:
inquiring the satellite data archives,
extracting the information/parameter from Earth Observation data using already developed scientific modules
producing numerical values or geo-coded thematic maps as products archived in the database system.
The End-User interface consists in a Web-GIS system where products, in vector or raster format, are visualized and
distributed according to the specific emergency phase.
A retrieval of tropospheric volcanic ash from Mt Etna has been carried out, using measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS). The NASA-MODIS satellite instrument acquires images in the 0.4 to 14 µm spectral range with a spatial resolution of 1 km at nadir. The eruption which occurred on 24 November 2006 is considered as a test case in this work. In order to derive the ash plume optical thickness, the particle effective radius and the total mass, the Brightness Temperature Difference procedure has been applied to MODIS channels 31 (centered at 11 µm) and 32 (centered at 12 µm). Channel 5 (centered at 1.24 µm) has been used to refine the cloud discrimination, exploiting the distinct reflectivity of meteorological and volcanic clouds in the near infrared spectral range. The detection of volcanic ash pixels has been significantly improved by applying an atmospheric water vapor correction to MODIS data. This procedure doubles the number of pixels identified as containing volcanic ash compared to the original method. The retrieved mean ash optical thickness at 0.55 µm, mean particle effective radius and the total ash mass in the plume are 0.4, 3.5 µm and 3620 tons, respectively. A detailed sensitivity analysis has been carried out to investigate errors in the retrieval caused by the uncertainty in various parameters: surface temperature and emissivity, plume geometry (altitude and thickness), ash type and atmospheric water vapor. Results show that the largest contributions to retrieval errors are from uncertainty in surface parameters, aerosol type and atmospheric water vapor. The total tropospheric volcanic ash retrieval errors are estimated to be 30%, 30% and 40% for mean AOT, mean effective radius and total mass retrieval, respectively.
KEYWORDS: MODIS, Geographic information systems, Synthetic aperture radar, Satellites, Sensors, Data processing, Computing systems, Visualization, Space sensors, Global Positioning System
The Project called Sistema Rischio Vulcanico (SRV) is funded by the Italian Space Agency (ASI) in the frame of the
National Space Plan 2003-2005 under the Earth Observations section for natural risks management. The SRV Project is
coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) which is responsible at national level for the
volcanic monitoring. The objective of the project is to develop a pre-operative system based on EO data and ground
measurements integration to support the volcanic risk monitoring of the Italian Civil Protection Department which
requirements and need are well integrated in the GMES Emergency Core Services program. The project philosophy is to
implement, by incremental versions, specific modules which allow to process, store and visualize through Web GIS tools
EO derived parameters considering three activity phases: 1) knowledge and prevention; 2) crisis; 3) post crisis. In order
to combine effectively the EO data and the ground networks measurements the system will implement a multi-parametric
analysis tool, which represents and unique tool to analyze contemporaneously a large data set of data in
"near real time". The SRV project will be tested his operational capabilities on three Italian Volcanoes: Etna,Vesuvio
and Campi Flegrei.
The volcanic ash detection procedures are based on Brightness Temperature Difference (BTD) algorithm using the
thermal infrared channels centred around 11 and 12 microns of a multispectral satellite sensor. The Mie code has been is
included in the retrieval procedure to compute the ash optical properties from the ash microphysical characteristics. The
simulations has been carried out using MODTRAN radiative transfer model. The Nasa-Modis and the Noaa-Avhrr
measurements of Mt. Etna eruptive plume occurred in November 2006 have been analyzed to retrieve the plume optical
thickness, the particle effective radius and the size distribution.
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