Climatology of dust aerosol size distribution and optical properties derived from remotely sensed data in the solar spectrum

Simultaneous spectral remote observations of dust properties from space and from the ground create a powerful tool for the determination of ambient dust properties integrated on the entire atmospheric column. The two measurement methods have a complementary sensitivity to variety of dust properties. The methodology is demonstrated using spectral measurements (0.47-2.21 mum) from Landsat (TM) over the bright Senegalian coast and dark ocean, and Aerosol Robotic Network (AERONET) radiances measured in several locations. We derive (1) the dust size distribution, showing a dominant coarse mode at 1-5 mum and a secondary mode around 0.5 mum effective radius; (2) dust absorption, which is found to be substantially smaller than reported from previous measurements; (3) the real part of the refractive index which varies within the range 1.53-1.46; and we show that (4) the effect of the dust nonspherical shape on its optical properties is not significant for scattering angles < 120 degrees.