Extraordinary dust event over Beijing, China, during April 2006:: Lidar, Sun photometric, satellite observations and model validation

An extraordinary dust event over Beijing ( April 2006) was followed by a synergy of lidar, Sun photometric and satellite measurements. Extreme aerosol optical depth (AOD) values ( 1 - 4) were measured by AERONET and MODIS over Beijing. The size distribution of the particles remained close to 2.5 mu m and the single scattering albedo was around 0.92 +/- 0.5 ( 440 nm). Coarse particles contributed to more than 60 - 80% to the AOD values, indicating the presence of very large particles (Angstrom exponent < 0.3). Coarse particle contribution to total AOD is associated with the free-tropospheric aerosols calculated by lidar profiles (65%). Lidar vertical profiles with AOD values from AERONET were used to estimate a typical lidar ratio for the dust particles ( 84 sr) during the most intense dust period. The DREAM forecast model was applied for the accurate description of the dust event evolution. Ground-truth data were used for the validation of DREAM over the Beijing area.