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Using conventional (single-polarization) radar data to assess attenuation due to rain on satellite-to-Earth paths requires the assumptions that the drops have a particular statistical distribution of sizes, and that the drops are of water. In the very localised regions of intense rain which influence such paths most severely, these assumptions can lead to large errors. This paper presents comparisons between direct measurements of attenuation and those computed using data from a dual-polarization radar technique. This technique can considerably reduce the errors of radar-derived estimates of attenuation. It also gives a clear distinction between ice and water.

A 10 cm (*) radar has been used on the steerable 25 m diameter aerial at Chilbolton, U.K., to produce detailed threedimensional maps of raincell distribution and intensity. The present paper examines differences in variation of radar reflectivity with height from the model at present recommended by theCcir.Wind shear can have a considerable influence on the distribution of rain as it falls, and may cause a 45° angle of inclination of a cell. This remains constant as the rain cell travels and is usually offset from the direction of travel of the cell. The information on the variation of radar reflectivity with height and the inclination of the rain cells are each important in the field of radio communications.