Linear polarization signatures of atmospheric dust with the SolPol direct-sun polarimeter
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Published:2023-10-12
Issue:19
Volume:16
Page:4529-4550
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Daskalopoulou VasilikiORCID, Raptis Panagiotis I.ORCID, Tsekeri AlexandraORCID, Amiridis VassilisORCID, Kazadzis SteliosORCID, Ulanowski ZbigniewORCID, Charmandaris Vassilis, Tassis KonstantinosORCID, Martin WilliamORCID
Abstract
Abstract. Dust particles in lofted atmospheric layers may present a
preferential orientation, which could be detected from the resulting
dichroic extinction of the transmitted sunlight. The first indications were
provided relatively recently on atmospheric dust layers using passive
polarimetry, when astronomical starlight observations of known polarization
were found to exhibit an excess in linear polarization, during desert dust
events that reached the observational site. We revisit the previous
observational methodology by targeting dichroic extinction of transmitted
sunlight through extensive atmospheric dust layers utilizing a direct-sun
polarimeter, which is capable to continuously monitor the polarization of
elevated aerosol layers. In this study, we present the unique observations
from the Solar Polarimeter (SolPol) for different periods within 2 years,
when the instrument was installed in the remote monitoring station of PANGEA
– the PANhellenic GEophysical observatory of Antikythera – in Greece. SolPol
records polarization, providing all four Stokes parameters, at a default
wavelength band centred at 550 nm with a detection limit of 10−7. We, overall, report on detected increasing trends of linear polarization,
reaching up to 700 parts per million, when the instrument is targeting away
from its zenith and direct sunlight propagates through dust concentrations
over the observatory. This distinct behaviour is absent on measurements we
acquire on days with lack of dust particle concentrations and in general of low aerosol content. Moreover, we investigate the dependence of the degree of linear polarization on the layers' optical depth under various dust loads
and solar zenith angles and attempt to interpret these observations as an
indication of dust particles being preferentially aligned in the Earth's
atmosphere.
Funder
State Scholarships Foundation H2020 European Research Council European Cooperation in Science and Technology A.G. Leventis Foundation Stavros Niarchos Foundation Staatssekretariat für Bildung, Forschung und Innovation Foundation for Research and Technology-Hellas
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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