ITU-R P.840-8 PDF

This Recommendation provides methods to predict the attenuation due to clouds and fog on Earth-space paths.

The ITU Radiocommunication Assembly,

considering

a) that there is a need to give guidance to engineers in the design of Earth-space telecommunication systems for frequencies higher than 10 GHz;

b) that attenuation due to clouds may be a factor of importance especially for microwave systems well above 10 GHz or low-availability systems;

c) that for the calculation of the time series of total attenuation and space-time prediction methods, an analytical expression for the statistics of the total columnar content of cloud liquid water is needed;

d) that local measured data of the total columnar content of cloud liquid water may not be available,

recommends

that if local measured data of the total columnar content of cloud liquid water is not available, the method given in § 3.1 of Annex 1 should be used for the prediction of the attenuation due to clouds and fog;

that if local measured data of the total columnar content of cloud liquid water is available, the method given in § 3.2 of Annex 1 should be used for the calculation of the attenuation due to clouds;

that the information in § 4 of Annex 1 should be used for global calculations of propagation effects, required by, inter alia, space-time channel models, that require an analytic expression for the statistics of the total columnar content of cloud liquid water.