Predicting cloud attenuation on Earth-space EHF links

This contribution presents a new approach to the prediction of cloud attenuation A on Earth-space links operating in the EHF (Extremely High Frequency) range. The methodology relies on SMOC (Stochastic MOdel of Clouds), which synthesizes high-resolution three-dimensional distributions of the liquid water content w (extent: 200 km×200 km horizontal, 10 km vertical), starting from coarse integral information typically provided by global gridded Numerical Weather Prediction products. Cloud attenuation statistics are calculated by coupling synthetic cloud fields with a simplified yet accurate approach to estimate cloud attenuation based on the concept of mass absorption coefficient. Tests performed against reference attenuation data inferred from an extensive set of radiosonde observations show a very satisfactory accuracy of the proposed methodology in estimating A and, on the other hand, a marked tendency to overestimation of the model currently adopted in recommendation ITU-R P.840-6.