Profiling Dust Mass Concentration in Northwest China Using a Joint Lidar and Sun-Photometer Setting

The satellite-based estimation of the dust mass concentration (DMC) is essential for accurately evaluating the global biogeochemical cycle of the dust aerosols. As for the uncertainties in estimating DMC caused by mixing dust and pollutants and assuming a fixed value for the mass extinction efficiency (MEE), a classic lidar-photometer method is employed to identify and separate the dust from pollutants, obtain the dust MEE, and evaluate the effect of the above uncertainties, during five dust field experiments in Northwest China. Our results show that this method is effective for continental aerosol mixtures consisting of dust and pollutants. It is also seen that the dust loading mainly occurred in the free troposphere (<6 km), with the average mass loading of 905 +/- 635 mu g m(-2) trapped in the planetary boundary layer. The dust MEE ranges from 0.30 to 0.60 m(2) g(-1) and has a significantly negative relationship with the size of dust particles. With the assumption of the dust MEE of 0.37 (0.60) m(2) g(-1), the DMC is shown to be overestimated (underestimated) by 20-40% (15-30%). In other words, our results suggest that the change of MEE with the size of dust particles should be considered in the estimation of DMC.