Dust transport and advection measurement with spaceborne lidars ALADIN and CALIOP and model reanalysis data
Authors: Dai Guangyao , Sun Kangwen , Wang Xiaoye , Wu Songhua , E Xiangying , Liu Qi , Liu Bingyi 
Published: June 2022

Abstract. In this paper, a long-term large-scale Saharan dust
transport event which occurred between 14 and 27 June 2020 is tracked
with the spaceborne lidars ALADIN (Atmospheric Laser Doppler
Instrument) and CALIOP (Cloud-Aerosol Lidar with Orthogonal
Polarization) together with ECMWF (European Centre for Medium-Range Forecasts) and HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory model) analysis. We evaluate the performance of ALADIN and CALIOP on the
observations of dust optical properties and wind fields and explore the
possibility of tracking the dust events and calculating the dust mass
advection with the combination of satellite and model data. The dust plumes
are identified with the AIRS/Aqua Dust Score Index and with the vertical
feature mask product from CALIOP. The emission, dispersion, transport and
deposition of the dust event are monitored using the data from AIRS/Aqua,
CALIOP and HYSPLIT. With the quasi-synchronized observations by ALADIN and
CALIOP, combined with the wind field and relative humidity, the dust
advection values are calculated. From this study, it is found that the dust
event generated on 14 and 15 June 2020 from the Sahara in North Africa
dispersed and moved westward over the Atlantic Ocean, finally being
deposited in the western Atlantic Ocean, the Americas and the Caribbean Sea.
During the transport and deposition processes, the dust plumes are trapped
in the northeasterly trade-wind zone between latitudes of 5∘ and 30∘ N and altitudes of 0
and 6 km. Aeolus provided the observations of the dynamics of this dust
transport event in the Saharan Air Layer (SAL). From the measurement results
on 19 June 2020, the dust plumes are captured quasi-simultaneously over the
emission region (Western Sahara), the transport region (middle Atlantic) and
the deposition region (western Atlantic) individually, which indicates that
the dust plume area over the Atlantic on the morning of this day is quite
enormous and that this dust transport event is massive and extensive. The
quasi-synchronization observation results of 15, 16, 19, 24 and 27 June by
ALADIN and CALIOP during the entire transport process show good agreement
with the Dust Score Index data and the HYSPLIT trajectories, which
indicates that the transport process of the same dust event is tracked by
ALADIN and CALIOP, verifies that the dust transport spent around 2 weeks
from the emission to the deposition and achieved the respective observations
of this dust event's emission phase, development phase, transport phase,
descent phase and deposition phase. Finally, the advection values for
different dust parts and heights on 19 June and on the entire transport
routine during transportation are computed. On 19 June, the mean dust
advection values are about 1.91±1.21 mg m−2 s−1 over the emission region,
1.38±1.28 mg  m−2 s−1 over the transport region and 0.75±0.68mgm-2s-1 over the
deposition region. In the whole lifetime of the dust event, the mean dust
advection values were about 1.51±1.03mgm-2s-1 on 15 June 2020, 2.19±1.72mgm-2s-1 on 16 June 2020, 1.38±1.28mgm-2s-1 on 19 June 2020, 1.60±1.08mgm-2s-1 on 24 June 2020 and 1.03±0.60mgm-2s-1 on 27 June 2020. During the dust development stage, the mean advection values gradually
increased and reached their maximum on 16 June with the enhancement of the
dust event. Then, the mean advection values decreased during the transport
and the deposition of the dust over the Atlantic Ocean, the Americas and the
Caribbean Sea.