Abstract
The spatiotemporal and especially the vertical distributions of dust aerosols play crucial roles in the climatic effect of dust aerosol. In the present study, the spatial-temporal distribution of dust aerosols over East Asia was investigated using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) retrievals (01/2007–12/2011) from the perspective of the frequency of dust occurrence (FDO), dust top layer height (TH) and profile of aerosol subtypes. The results showed that a typical dust belt was generated from the dust source regions (the Taklimakan and Gobi Deserts), in the latitude range of 25°N~45°N and reaching eastern China, Japan and Korea and, eventually, the Pacific Ocean. High dust frequencies were found over the dust source regions, with a seasonal sequence from high to low as follows: spring, summer, autumn and winter. Vertically, FDOs peaked at about 2 km over the dust source regions. In contrast, FDOs decreased with altitude over the downwind regions. On the dust belt from dust source regions to downwind regions, the dust top height (TH) was getting higher and higher. The dust TH varied in the range of 1.9–3.1 km above surface elevation (a.s.e.), with high values over the dust source regions and low values in the downwind areas, and a seasonally descending sequence of summer, spring, autumn and winter in accord with the seasonal variation of the boundary layer height. The annual AOD (Aerosol Optical Depth) was generally characterized by two high and two low AOD centers over East Asia. The percent contribution of the Dust Aerosol Optical Depth to the total AOD showed a seasonal variation from high to low as follows: spring, winter, autumn and summer. The vertical profile of the extinction coefficient revealed the predominance of pure dust particles in the dust source regions and a mixture of dust particles and pollutants in the downwind regions. The dust extinction coefficients over the Taklimakan Desert had a seasonal pattern from high to low as follows: spring, winter, summer and autumn. The results of the present study offered an understanding of the horizontal and vertical structures of dust aerosols over East Asia and can be used to evaluate the performance aerosol transport models.
Highlights
Dust aerosol, one of the most important aerosol species, modifies the energy balance and the hydrologic cycle directly by absorbing and scattering solar radiation and indirectly by altering cloud microphysical properties [1,2,3]
By analyzing spatial patterns of Aerosol Optical Depth (AOD), dusts to the total AOD (D_AOD) and profiles of extinction coefficients of various aerosol types, we further investigated into long-distance dust transport, which is known to impact the public health of populated centers in eastern China, Korea and Japan
The present study analyzed the seasonal variation of dust aerosols and transport over East Asia using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) retrievals
Summary
One of the most important aerosol species, modifies the energy balance and the hydrologic cycle directly by absorbing and scattering solar radiation and indirectly by altering cloud microphysical properties [1,2,3]. Previous work using aircraft, upper-air sounding balloons and ground-based platforms are limited in space and time, offering little information on the vertical structure of dust aerosols These limitations have been partially addressed with the launch of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite [13,14]. Human health concerns and policy on pollution controls require detailed knowledge of the speciation of dust (pure dust versus dust mixed with biomass burning smoke) and the mean behaviors of total dust (sum of pure and polluted dust) Another related study documented the seasonal variations of the aerosol extinction profile and occurrence frequency using five-year Level 3 CALIPSO products, focusing on global patterns [15].
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