Attenuation of Terahertz Waves by Wet Sn Ow, Dry Snow and Rain

Abstract

The technology of terahertz (THz) waves offer wide bandwidth and high capacity for future wireless communications. However, THz waves also suffer from high sensitivity to adverse weather conditions when propagating in the near-surface atmosphere. There have been several systematic studies conducted on this under different weather conditions such as rain, fog, haze, cloud and air turbulence. In particular, several investigations of the scattering performance of terahertz waves in snow have been reported [1]. But, there is still a lack of systematic studies because of the difficulties in measurements and characterizations due to the complicate shapes of snow particles. Therefore, a combined approach relying on both theoretical models and case studies is valuable. In this work, we combine meteorological data and Mie scattering theory to investigate the scattering behavior of THz waves in falling snow and in a snow layer. The theoretical results are in rough qualitative agreement with the experimental data when gaseous attenuation and scintillation effect are not considered. Compared with the attenuation by rain, the THz signal suffers higher loss when propagates in dry and wet snow for frequencies above 200 GHz. Signal loss in dry snow layer is mainly attributed to scattering effects because of the low water content, and it doesn't change when the temperature is reduced from 0 to -20 oC. The absorption effect becomes more serious when snow wetness increases, but the scattering effect is largely unaffected by water content.