Research Papers

Mt. Etna tropospheric ash retrieval and sensitivity analysis using moderate resolution imaging spectroradiometer measurements

[+] Author Affiliations
Stefano Corradini, Claudia Spinetti

Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, Rome, Italy 00143 Italy

Elisa Carboni

Atmospheric Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road Oxford OX1, Oxford, United Kingdom 3PU United Kingdom

Cecilia Tirelli

Dipartimento di Fisica, Universita degli Studi di Roma, Piazzale Aldo Moro 5, Rome, Italy 00185 Italy

Maria F. Buongiorno

Remote Sensing Lab, Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, Rome, Italy 00143 Italy

Sergio Pugnahi, Gabriele Gangale

Dipartimento di Ingegneria Materiali e Ambiente, Universita di Modena e Reggio Emilia, Via Vignolese 905, Modena, Italy 41100 Italy

J. Appl. Remote Sens. 2(1), 023550 (November 21, 2008). doi:10.1117/1.3046674
History: Received December 20, 2007; Revised November 18, 2008; Accepted November 18, 2008; November 21, 2008; Online November 21, 2008
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Abstract

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.

© 2008 Society of Photo-Optical Instrumentation Engineers

Topics

MODIS

Citation

Stefano Corradini ; Claudia Spinetti ; Elisa Carboni ; Cecilia Tirelli ; Maria F. Buongiorno, et al.
"Mt. Etna tropospheric ash retrieval and sensitivity analysis using moderate resolution imaging spectroradiometer measurements", J. Appl. Remote Sens. 2(1), 023550 (November 21, 2008). ; http://dx.doi.org/10.1117/1.3046674


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