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A HIGH-RESOLUTION SIMULATION OF
CONVECTIVE-SCALE TRANSPORT OF
DUST AEROSOL AND ITS REPRESENTATION
IN CLOUD-RESOLVING SIMULATIONS
TETSUYA TAKEMI
Disaster Prevention Research Institute, Kyoto University,
Gokasho, Uji, Kyoto 611-0011, Japan,
takemi@storm.dpri.kyoto-u.ac.jp
Boundary-layer processes under fair weather conditions play a significant role
in the global budget of dust aerosols. Representing such small-scale processes
are critical for better simulating dust transport in large-scale models. This
study examines the microscale transport of dust aerosol due to convection by
performing a high-resolution simulation and the sensitivity of the convective-
scale dust transport to horizontal grid spacing of the order of 1 km typically
used in cloud-resolving simulations. Turbulence effects play a significant role
in raising and mixing dust aerosol within the boundary layer and cumulus
convection transports dust further upward. A significant difference in the
simulated dust transport is found between the simulations with the 4-km grid
and the finer grid spacings. Through conducting the sensitivity simulations, we
propose a simple formulation using an eddy velocity scale in order to represent
both shallow and deep convection and hence to better reproduce dust emission
and transport in cloud-resolving simulations.
1. Introduction
The transport of mineral dust aerosols in a desert region is regulated not
only by synoptic-scale and mesoscale disturbances but also by smaller-scale
processes such as boundary-layer turbulence and cloud-scale convection.
Diurnal variability is significant for these small-scale processes especially
under fair weather conditions. Luo
et al.
1
showed that the diurnal variability
of dust mobilization and concentration is responsible for 20% up to 80%
of the total temporal variability over desert regions. Koch and Renno
2
estimated that boundary-layer convective motion contributes to about
35% of the global dust budget. The low-level transport due to convective
injection from the planetary boundary layer (PBL) into the free troposphere
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