Numerical simulations of Asian dust storms using a coupledclimate-aerosol microphysical model

摘要

We have developed a three-dimensional coupled microphysical/climate model basedon the National Center for Atmospheric Research Community Atmospheres Model andthe University of Colorado/NASA Community Aerosol and Radiation Model forAtmospheres. We have used the model to investigate the sources, removal processes,transport, and optical properties of Asian dust aerosol and its impact on downwindregions. The model simulations are conducted primarily during the time frame of theAerosol Characterization Experiment–Asia field experiment (March–May 2001) sinceconsiderable in situ data are available at that time. Our dust source function followsGinoux et al. (2001). We modified the dust source function by using the friction velocityinstead of the 10-m wind based on wind erosion theory, by adding a size-dependentthreshold friction velocity following Marticorena and Bergametti (1995) and by adding asoil moisture correction. A Weibull distribution is implemented to estimate thesubgrid-scale wind speed variability. We use eight size bins for mineral dust ranging from0.1 to 10 pm radius. Generally, the model reproduced the aerosol optical depth retrievedby the ground-based Aerosol Robotic Network (AERONET) Sun photometers at sixstudy sites ranging in location from near the Asian dust sources to the Eastern Pacificregion. By constraining the dust complex refractive index from AERONET retrievals nearthe dust source, we also find the single-scattering albedo to be consistent with AERONETretrievals. However, large regional variations are observed due to local pollution. Thetiming of dust events is comparable to the National Institute for Environmental Studies(NIES) lidar data in Beijing and Nagasaki. However, the simulated dust aerosols are athigher altitudes than those observed by the NIES lidar.