Abstract. We coordinated a ground-based network that has been in use since 1997 to observe Asian dust during springtime. Huge Asian dust events that occurred in the middle of April 1998 were captured by this network. In this paper we present the organization of the network; a description of the instruments, including the lidar, sky radiometer, and optical particle counter; and the results of the observation, and offer discussions regarding the transport mechanism of Asian dust in east Asia using an on-line tracer model. We discussed the time series of the surface concentration and the height distribution of the dust. A cutoff cyclone generated during the dust episode was responsible for trapping and sedimentation during the transportation of the Asian dust, particularly in the southern parts of China and Japan. Horizontal dust images derived from NOAA/AVHRR clearly revealed the structure of the vortex. The lidar network observation confirmed the general pattern of dust height distribution in this event; the height of the major dust layer was about 3 km over Japan but was higher (4 to 5 km) in Seoul and Hefei. A thin dust layer in the upper troposphere was also commonly observed in Hefei and Japan. Evidence of the coexistence of dust and cirrus was shown by the polarization lidar. The lidar network observation of Asian dust and satellite remote sensing provide key information for the study of the transport mechanism of Asian dust. Further extension of the lidar network toward the interior of the continent and the Pacific Rim would reveal the greater global mechanism of the transportation.
[1] A Mie lidar was used to make observations of Asian dust over Hefei (31.90°N, 117.16°E) in spring 2000. This paper presents main features of vertical distribution and temporal variation of Asian dust extinction coefficient at 532-nm wavelength. It was found that the Asian dust events contributed significantly to very large aerosol extinction coefficients in the boundary layer or middle troposphere. Extinction coefficient value as large as 0.7 km À1 at 3 km above ground level (AGL) has been observed. The Asian dust extinction coefficient profiles showed very big changes from early morning to evening and also appeared substantial amount of temporal variation during the nighttime. For the severe Asian dust days the depth of boundary layer rose up to around 4 km AGL, but only 1$2 km AGL for normal days. The seasonal average aerosol extinction coefficient profiles also showed that larger aerosol extinction coefficients from 1-to 10-km altitude range were observed in the springtime rather than in any other season. Meanwhile, solar extinction and radiation measurements indicated that the Asian dust particles were composed of larger size particles and they produced significantly perturbation in solar radiation on the Earth surface.
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