Record-breaking dust loading during two mega dust storm events over northern China in March 2021: aerosol optical and radiative properties and meteorological drivers
Authors: Gui Ke , Yao Wenrui , Che Huizheng , An Linchang , Zheng Yu , Li Lei , Zhao Hujia , Zhang Lei , Zhong Junting , Wang Yaqiang , Zhang Xiaoye 
Published: June 2022

Abstract. Although a remarkable reduction in the frequency of sand
and dust storms (SDSs) in the past several decades has been reported over
northern China (NC), two unexpected mega SDSs occurred on 15–20 and 27–29 March 2021 (abbreviated as the “3.15” and “3.27” SDS
events), which has reawakened widespread concern. This study characterizes
the optical, microphysical, and radiative properties of aerosols and their
meteorological drivers during these two SDS events using the Sun photometer
observations in Beijing and a comprehensive set of multiple satellite
(including MODIS, VIIRS, CALIOP, and Himawari-8) and ground-based
observations (including the CMA visibility network and AD-Net) combined with
atmospheric reanalysis data. Moreover, a long-term (2000–2021) dust optical
depth (DOD) dataset retrieved from MODIS measurements was also utilized to
evaluate the historical ranking of the dust loading in NC during dust
events. During the 3.15 and 3.27 events, the invasion of dust plumes greatly
degraded the visibility over large areas of NC, with extreme low visibility
of 50 and 500 m recorded at most sites on 15 and 28 March, respectively.
Despite the shorter duration of the 3.27 event relative to the 3.15 event,
sun photometer and satellite observations in Beijing recorded a larger peak
AOD (∼2.5) in the former than in the latter (∼2.0), which was mainly attributed to the short-term intrusion of coarse-mode
dust particles with larger effective radii (∼1.9 µm)
and volume concentrations (∼2.0 µm3 µm−2) during the 3.27 event. The shortwave direct aerosol radiative
forcing induced by dust was estimated to be −92.1 and −111.4 W m−2 at the top of the atmosphere, −184.7 and −296.2 W m−2 at
the surface, and +92.6 and +184.8 W m−2 in the atmosphere in
Beijing during the 3.15 and 3.27 events, respectively. CALIOP observations
show that during the 3.15 event the dust plume was lifted to an altitude of
4–8 km, and its range of impact extended from the dust source to the
eastern coast of China. In contrast, the lifting height of the dust plume
during the 3.27 event was lower than that during the 3.15 event, which was also
confirmed by ground-based lidar observations. The MODIS-retrieved DOD data
registered these two massive SDS events as the most intense episode in
the same period in history over the past 2 decades. These two extreme SDS
events were associated with both atmospheric circulation extremes and local
meteorological anomalies that favored enhanced dust emissions in the Gobi
Desert (GD) across southern Mongolia and NC. Meteorological analysis
revealed that both SDS events were triggered by an exceptionally strong
Mongolian cyclone generated at nearly the same location (along the central
and eastern plateau of Inner Mongolia) in conjunction with a surface-level
cold high-pressure system at the rear, albeit with differences
in magnitude and spatial extent of impact. In the GD, the early melting of
spring snow caused by near-surface temperature anomalies over dust source
regions, together with negative soil moisture anomalies induced by decreased
precipitation, formed drier and barer soil surfaces, which allowed for
increased emissions of dust into the atmosphere by strongly enhanced surface
winds generated by the Mongolian cyclone.