Optical Properties of the Turbid Atmosphere in the Yellow Sand Event Over Japan

The optical properties of yellow sand particles were examined by comprehensive measurements carried out during the period of April 21–May 12, 1982 in Nagasaki, Japan. In situ measurements of the phase functions of aerosols were performed for both parallel and perpendicularly polarized components with a portable polar nephelometer, as well as spectral extinction measurements with a sunphotometer, and measurements of the aureole intensity with an aureolemeter. Large depolarization ratio values of about 0.3 and a power-law size distribution with an exponent around 3.0 were characteristically found in the yellow sand event, indicating an abundance of large, irregular sand particles. On the other hand, a powerlaw size distribution with an exponent of around 4.0, i. e., a typical Junge distribution, was well developed in the atmosphere for normal conditions over Japan. The size spectrum and complex index of refraction of aerosols retrieved from the light scattering measurements were found to be useful in parameterizing the phase functions of yellow sand particles, although an unrealistically large value was retrieved for the imaginary index of refraction.