Lidar observations of Asian dust over Hefei, China, in spring 2000

Abstract

[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.

Profiling the PM<sub>2.5</sub> mass concentration vertical distribution in the boundary layer

“…The nearest urban influence is 15 km; therefore, the site is close enough to be influenced by local urban aerosols depending on wind direction. And in spring, dust aerosol from the northern/northwest regions of China may also affect this site (Zhou et al, 2002). So, five different aerosol types are considered in Fig.…”

Particulate air pollution in Lanzhou China

“…This is caused by the transport of the TSP due to dust storms. Recent studies indicate that dust storms originated in the East Asia not only influence air pollution in the origins and their neighboring regions Murayama et al, 2001;Sun et al, 2001;Zhou et al, 2002), but also have a long-distance effect across Pacific by atmospheric circulation (Husar et al, 2001;Tratt et al, 2001;Sun et al, 2001;Laat et al, 2001;Clarke et al, 2001). The major sources of the dust storms are the Gobi desert in Mongolia and northern China and Taklimakan desert in western China (Sun et al, 2001).…”

12-year LIDAR Observations of Tropospheric Aerosol over Hefei (31.9°N, 117.2°E), China

“…The Fernald method is applied to the joined signal profile to retrieve the aerosol backscatter coefficient [7], and three assumptions have to be made [5]: (1) The extinctionto-backscatter ratio (i.e. LIDAR ratio) for tropospheric aerosol is assumed constant with altitude and equal to 50 sr at 532 nm wavelength; (2) Molecular backscatter coefficient and extinction are calculated from a standard atmosphere model using Rayleigh scattering theory; (3) The boundary value is determined by assuming the aerosol backscattering ratio to be 1.01 for 532 nm at calibration height, where the atmosphere is very clean, calibration height is often determined around the tropopause according to LIDAR received signal with range-square and molecular backscatter corrections.…”

“…A Mie scattering LIDAR has been operated for profiling tropospheric aerosol since 1998 in Hefei (31.9°N, 117.2°E) [5,6]. Hefei is in the region between the Huaihe River and the Yangtse River, in the vicinity of the Yangtse delta.…”