Modeling coarse and giant desert dust particles
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Published:2022-09-29
Issue:18
Volume:22
Page:12727-12748
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Drakaki EleniORCID, Amiridis Vassilis, Tsekeri Alexandra, Gkikas AntonisORCID, Proestakis EmmanouilORCID, Mallios SotiriosORCID, Solomos Stavros, Spyrou ChristosORCID, Marinou EleniORCID, Ryder Claire L.ORCID, Bouris Demetri, Katsafados Petros
Abstract
Abstract. Dust particles larger than 20 µm in diameter have been
regularly observed to remain airborne during long-range transport. In this
work, we modify the parameterization of the mineral dust cycle in the
GOCART-AFWA dust scheme of WRFV4.2.1 to also include such coarse and giant particles, and we further discuss the underlying misrepresented physical
mechanisms which hamper the model in reproducing adequately the transport of
the coarse and giant mineral particles. The initial particle size
distribution is constrained by observations over desert dust sources.
Furthermore, the Stokes drag coefficient has been updated to account for realistic dust particle sizes (Re < 105). The new code was
applied to simulate dust transport over Cabo Verde in August 2015 (AER-D campaign). Model results are evaluated against airborne dust measurements
and the CALIPSO-LIVAS pure dust product. The results show that the modeled lifetimes of the coarser particles are shorter than those observed. Several
sensitivity runs are performed by reducing artificially the particles'
settling velocities in order to compensate underrepresented mechanisms, such
as the non-spherical aerodynamics, in the relevant parameterization schemes.
Our simulations reveal that particles with diameters of 5.5–17 and
40–100 µm are better represented under the assumption of an 80 % reduction in the settling velocity (UR80), while particles with sizes ranging between 17 and 40 µm are better represented in a 60 %
reduction in settling velocity (UR60) scenario. The overall statistical
analysis indicates that the best agreement with airborne in situ measurements downwind (Cabo Verde) is achieved with a 40 % reduction in settling velocity (UR40). Moreover, the UR80 experiment improves the
representation of the vertical structure of the dust layers as those are
captured by the CALIPSO-LIVAS vertically resolved pure dust observations. The current study highlights the necessity of upgrading the existing model
parameterization schemes of the dust life-cycle components towards improving
the assessment of the dust-related impacts within the Earth–atmosphere system.
Funder
Hellenic Foundation for Research and Innovation Deutscher Akademischer Austauschdienst Sight Research UK H2020 European Research Council
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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