Abstract
In bad weather conditions, e.g. rainy, foggy, and snowy conditions, exact slant visual ranges should be obtained for safe landings at airports. However, no equipment for achieving this has been installed in airports yet. In this study, the laser radar system is refined for estimating the slant visual range. It is found that the empirical data in bad weather conditions do not correspond to predictions with the current laser radar equation. Therefore, a new laser radar equation, which considers the divergence of the transmitting laser beam, is proposed. The slopes of this equation correspond well to the empirical data in various weather conditions. The visibilities estimated by this equation also correspond with those obtained by the slant transmittance system. Also, the extent of the divergence is examined by means of classifying the empirical data by weather conditions. As a result, it is found that the divergence of the transmitted laser beam increases in the order of rain, fog, misty rain, and snow.
