11-GHz Radio: Nationwide Long-Term Rain Rate Statistics and Empirical Calculation of 11-GHz Microwave Rain Attenuation

An important problem in designing terrestrial and earth-satellite radio systems at frequencies above 10 GHz is the added path attenuation caused by rain. Long term (>20 years) rain rate statistics are needed to engineer radio paths for various geographic locations to meet reliability objectives. Section II describes a method to obtain 20-year distributions of 5-minute point rain rates from the excessive short duration rainfall data1-2 for locations in the relatively wet eastern and midwestern U.S.A. Section III describes another method, employing the theory of extreme value statistics, to obtain 50-year distributions of 5-minute point rain rates from rainfall-intensity-duration-frequency curves 3 for locations in relatively dry locations such as western U.S.A. Section IV discusses the variability of rain rate distributions with observation time base. 1581 Table I -- Thresholds* of excessive short-duration rainfalls Minimum depth of recorded rainfall, inches 0.25 0.30 0.35 0.40 0.50 0.65 0.80 1.20 1.40 1.70 2.00 1.00