Radiative and dynamic effects of absorbing aerosol particles over the Pearl River Delta, China

Results are reported from a ground-based measurement campaign conducted in a highly polluted region in southeast of China in October–November 2004. The experiment focused on absorbing aerosol particles and their effects on the solar radiation field and local meteorology. A Raman lidar in conjunction with Sun photometer data measured profiles of particle extinction; ground-based in situ data of aerosol optical properties were collected by nephelometer and absorption photometer. Exceptionally high values of aerosol optical depth of up to 1.5 were observed.The measurements were input to a radiative transfer model, which simulated high solar radiative forcing values for the aerosol particles of up to -160Wm-2 at the ground (daily average) for the observed particle single-scattering albedo of 0.85. Maximum solar heating rates of 7–8Kday-1 were simulated at the top of the aerosol layer.The radiative simulations were used to drive a dynamic model of the planetary boundary layer (PBL). With this model the temporal course of the height of the PBL was simulated and compared with respective lidar data. The results show that the height of the PBL is significantly decreased due to the warming of the aerosol particles at the top of the PBL. In this way, the stabilizing effect of absorbing aerosol particles within the PBL was confirmed by a combination of experimental and modeling means.