Visibility Measurement Using Geometrical Optics Approximation in Rainy Day

The geometrical optics approximation (GOA) method is presented to measure atmospheric visibility of rainy day. The imaginary part of refractive complex has more influences on the extinction and absorption of raindrop, but has almost no influence on the scattering of raindrop. In rainy day, when the rainfall rate increases, the visibility curves of MIE and GOA are in good agreement, but the calculation speed in GOA is faster than Mie theory on the extinction coefficient of raindrop and visibility measurement in rainy day.