Regional Impact of Inter-Continental Aerosol Transport

In this paper, we present results showing the usefulness of multi-wavelength lidar measurements to study the interaction of aerosols in the PBL with long range advected aerosol plumes. In particular, our measurements are used to determine the plume angstrom exponent, which allows us to differentiate smoke events from dust events, as well as partitioning the total aerosol optical depth obtained from a CIMEL sky radiometer between the PBL and the high altitude plumes. Furthermore, we show that only if the optical depth from the upper level plumes is taken into account, the correlation between the lidar derived PBL aerosol optical depth and surface PM2.5 is high. In addition, we also observe the dynamic interaction of high altitude plumes interacting with the PBL, resulting in a dramatic rise in surface PM10 concentrations without a corresponding dramatic rise in PM2.5 concentrations. These observations strongly suggest the deposition of large particulates into the PBL which is consistent with both lidar angstrom coefficient measurements and back-trajectory analysis. These studies are useful in identifying the vertical length scales in which spaced based lidars such as Calipso can be used to probe surface PM2.5.