Abstract

Desert aerosol size distribution measurements taken at China Lake, CA, along with a wind-blown dust model from AFGL indicate that desert dust consists of three lognormally distributed modes. The smallest, composed of combustion products, peaks at a diameter of 0.1 μm. An intermediate mode, composed of dust, peaks at 0.6 μm, the largest particles being 10 μm. These modes are wind speed independent. The largest particle mode peaks at 10 μm depending on wind speed. Attenuation for these aerosols may not follow Beer’s law for short wavelengths because of forward scattering generated by the larger particles. This work ascertains those conditions for which forward scattering is important by computing an effective extinction coefficient for a 1-km path over the spectral range of 0.4–12 μm as a function of wind speed and visibility and graphically comparing it to the Mie computed extinction coefficient.

© 1988 Optical Society of America