Weather measurement system using near-infrared differential spectroscopy

A weather measurement system was constructed using near-infrared light-emitting diodes and indium gallium arsenide photodiodes for the 1-2 μm near-infrared region. The difference in the absorbance of water for near-infrared light at wavelengths of 945 and 1450 nm was used to distinguish between three different precipitation types: snow, sleet and rain. From the ratio of the number of generated light absorption events at the two wavelengths, a distinction between snow, sleet and rain events was demonstrated. The judgement results by this system were consistent with those obtained from the meteorological observatory weather database.