Analysis of variations in factors of specific absorption of sub-terahertz waves in the earth’s atmosphere

The problem of absorption of sub-THz waves in the Earth's atmosphere is well-known to hinder radio astronomy and telecommunication. This absorption is mostly defined by water and oxygen content over the eye beam. We are presenting an analysis of variations in the specific absorption factors which are responsible for interrelation between the sub-THz optical depth, precipitable water vapor and altitude of the site. These factors depend mostly on the height, atmospheric temperature distribution over height, and overall weather conditions. Therefore, for a correct estimation of the optical depth based on weather data one will need to calculate these factors thoroughly for the specific site and time of the year. We have analyzed the height and weather dependencies of the factors for different seasons and frequencies. A comparison of absorption estimations according to different models and databases such as MPM Liebe, Moliere, JPL catalog lines, HITRAN lines and Pardo2001 continua has demonstrated a discrepancy in the results. A comparison of estimated and experimental values found in the literature is presented.