Two methods for predicting year-to-year variability of rain rate are discussed. Results using one of the methods were presented in this TRANSACTIONS in May 1979. Contour maps illustrating the year-to-year standard deviation for the U.S.A., using the second method, are presented. A comparison of both methods with some observational data is included.

Further extensions of the Rice-Holmberg rainfall prediction model are reported. These extensions describe the variation of rainfall with location in the U.S.A., as well as the standard deviation of their year-to-year variation. Application to the prediction of microwave signal attenuation by rainfall, and the comparison with observed data are illustrated.

Recent progress is reported for extensions of the RiceHolmberg rainfall-prediction model. This extension provides for the year-to-year variation expected for rainfall and is required to permit any useful comparison of predicted with observed rainfall (or predicted with observed microwave attenuation due to rainfall). The results are illustrated for Europe.

During November 1971, a 400 Mbit/s quadriphase-shift-keyed system was operated at 13.3 and 14.9 GHz over a 22.8-km line-of-sight path. This path was chosen because of its high incidence of meteorological conditions favorable to anomalous propagation. Performance of the system during fading periods is reported here. Additional information from extensive meteorological measurements near midpath is presented to identify the source of the fading. The dual frequency measurements for spaced receiving antennas indicate that diversity reception, properly implemented, would have provided an effective fading remedy.