Mt. Etna aerosol optical thickness from MIVIS images

M. Remitti, S. Pugnaghi, S. Teggi

Abstract


This work focuses on the evaluation of Aerosol Optical Thickness (AOT) in Mt. Etna volcano area starting from
the analysis of MIVIS VIS images. MIVIS images and ancillary data (atmospheric profiles, photometric measurements,
atmospheric infrared radiances, surface temperatures, ground reflectances, SO2 abundances) were collected
during the «Sicily 97» campaign. Data elaboration was performed with extensive use of 6S radiative transfer model,
determining optical thickness with an inversion algorithm that uses atmospheric vertical profile, ground reflectance
data and radiance measured by the first MIVIS spectrometer (channels 1-20; range 0.44-0.82 n). Ground
reflectance is the most problematic parameter for the algorithm. In order to have a low and uniform surface reflectance,
only pixels located at an altitude between 2000-3000 m a.s.l. were analysed. At this altitude,AOT is very
low during non-eruptive periods: at Torre del Filosofo (2920 m a.s.l.) on June 16th 1997, during one MIVIS flight,
AOT at 0.55 n was 0.19. The uncertainty about ground reflectance produces significant errors on volcanic background
AOT, and in some cases the error is up to 100%. The developed algorithm worked well on volcanic plume,
allowing us to determine the plume related pixelsAOT. High plume AOT values minimize the problems deriving
from reflectance uncertainty. Plume optical thickness shows values included in a range from 0.5 to 1.0. The plume
AOT map of Mt. Etna volcano, derived from a MIVIS image of June 16th 1997, is presented.

Keywords


remote sensing;aerosol optical thickness;Mt. Etna volcano;MIVIS;6S

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References


DOI: https://doi.org/10.4401/ag-3164
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X