The scattering effects on the visibility measurements of laser transmissometer in rain and fog

Abstract A laser transmissometer is regarded as a promising visibility meter used in airports around the world. Based on the particle size distributions of rain and fog, we have numerically simulated the transmissions of photons through rain and fog using the Monte-Carlo method. The visibility errors induced by the single and multiple-scattering effects are discussed for different configurations of the optical system, considering the particle size distributions of the rain and fog. The simulation results show that the single scattering is the main factor introducing the visibility errors, and the multiple-scattering effect may be not negligible, especially for the low-visibility atmosphere, e.g., fog. Our simulation results further reveal that reducing the receiver aperture and increasing the baseline length of the optical system may effectively suppress the visibility errors caused by the scattering effects, which gives us important considerations on the design of the optical systems of the laser transmissometer.