Chenbo Xie

Lidar network observations of tropospheric aerosols

Observations of tropospheric aerosols (mineral dust, air-pollution aerosols, etc.) and clouds are being conducted using a network of two-wavelength (1064nm, 532nm) polarization (532nm) lidars in the East Asian region. Currently, the lidars are operated continuously at 23 locations in Japan, Korea, China, Mongolia and Thailand. A real-time data processing system was developed for the network, and the data products such as the attenuated backscatter coefficients and the estimated extinction coefficients for non-spherical and spherical aerosols are generated automatically for online network stations. The data are used in the real-time monitoring of Asian dust as well as in the studies of regional air pollution and climate change.

Characteristics of aerosol optical properties in pollution and Asian dust episodes over Beijing, China

Aerosol optical properties were continuously measured with the National Institute for Environmental Studies (NIES) compact Raman lidar over Beijing, China, from 15 to 31 December 2007. The results indicated that in a moderate pollution episode, the averaged aerosol extinction below 1 km height was 0.39+/-0.15 km(-1) and the lidar ratio was 60.8+/-13.5 sr; in heavy pollution episode, they were 1.97+/-0.91 km(-1) and 43.7+/-8.3 sr; in an Asian dust episode, they were 0.33+/-0.11 km(-1) and 38.3+/-9.8 sr. The total depolarization ratio was mostly below 10% in the pollution episode, whereas it was larger than 20% in the Asian dust episode. The distinct characteristics of aerosol optical properties in moderate and heavy pollution episodes were attributed to the difference in air mass trajectory and the ambient atmospheric conditions such as relative humidity.

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

12-year LIDAR observations of tropospheric aerosol vertical distribution using a Mie scattering LIDAR in Hefei (31.9°N, 117.2°E) from 1998 to 2009 are presented and analyzed in this paper. Characters of temporal variation and vertical distribution of tropospheric aerosol over Hefei are summarized from the LIDAR measurements. The impacts of natural source and human activities on the aerosol vertical distribution over Hefei could be seen clearly. Dust particles from the north in spring could affect the aerosol distributions below about 12 km over Hefei, and aerosol scale height in April reaches 2.29±0.68 km. Both LIDAR measurements and surface visibility imply that aerosols in the lower troposphere have been increasing since about 2005.

Measurements of aerosol phase function and vertical backscattering coefficient using a charge-coupled device side-scatter lidar

By using a charge-coupled device (CCD) as the detector, side-scatter lidar has great potential applications in the near range atmospheric detection. A new inversion method is proposed for CCD side-scatter lidar (Clidar) to retrieve aerosol phase function and vertical backscattering coefficient. Case studies show the retrieved results from Clidar are in good agreements with those obtained from other instruments. It indicates that the new proposed inversion method is reliable and feasible and that the Clidar is practicable.

Aerosol Observation with Raman LIDAR in Beijing, China

Aerosol observation with Raman LIDAR in NIES (National Institute for Environmental Studies, Japan) LIDAR network was conducted from 17 April to 12 June 2008 over Beijing, China. The aerosol optical properties derived from Raman LIDAR were compared with the retrieved data from sun photometer and sky radiometer observations in the Aerosol Robotic Network (AERONET). The comparison provided the complete knowledge of aerosol optical and physical properties in Beijing, especially in pollution and Asian dust events. The averaged aerosol optical depth (AOD) at 675 nm was 0.81 and the Angstrom exponent between 440 nm and 675 nm was 0.99 during experiment. The LIDAR derived AOD at 532 nm in the planetary boundary layer (PBL) was 0.48, which implied that half of the total AOD was contributed by the aerosol in PBL. The corresponding averaged LIDAR ratio and total depolarization ratio (TDR) were 48.5sr and 8.1%. The negative correlation between LIDAR ratio and TDR indicated the LIDAR ratio decreased with aerosol size because of the high TDR associated with nonspherical and large aerosols. The typical volume size distribution of the aerosol clearly demonstrated that the coarse mode radius located near 3 lTEXg

Method and analysis of calculating signal-to-noise ratio in lidar sensing

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Backscatter by azimuthally oriented ice crystals of cirrus clouds.

l/TEXg in dust case, a bi-mode with fine particle centered at 0.2 lTEXg

New experimental method for lidar overlap factor using a CCD side-scatter technique

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Characteristic analysis of atmospheric boundary layer and particulate matter in Beijing

l/TEXg and coarse particle at 2 lTEXg

Cirrus cloud properties measurement using lidar in Beijing

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