Meteorological conditions and structures of atmospheric boundary layer in October 2004 over Pearl River Delta area
High-level concentrations of air pollutants usually occur in autumn and winter over Peal River Delta (PRD), China. Atmospheric boundary layer observations were carried out at Qingyuan, Panyu and Xinken in PRD in October 2004. Wind speed, wind direction, air temperature and aerosol characteristics were measured by radio soundings and Raman LIDAR. The observational results showed that surface high-pressure system (anti-cyclone), descent motion outside of hurricane and sea breeze would result in the high-level concentrations. The averaged height of atmospheric boundary layer in nighttime was about 200 m, while in day time the maximal value was about 1200 m. The aerosol layer typically reached up to 1.5-3.0 km. The averaged aerosol optical depth was 0.91 at 532 nm wavelength and aerosol mainly originated from fossil fuel and biomass-burning emissions. The presence of anti-cyclone high-pressure systems and sea breeze lead to the formation of three inversion layers and two aerosol layers as well as quite specific vertical profiles of the wind velocity over Xinken station.