Prediction of slant path rain attenuation statistics at various locations

Abstract

A method is described here for predicting attenuation statistics as a function of frequency and elevation angle at various locations. This method uses median reflectivity factor-height profiles as measured with radar. The zenith attenuations for each profile are calculated assuming a Laws and Parsons drop size distributioa. These attenuations are tied to the ground point rain rate and the corresponding probability exceedance levels as measured using long term raingauge data for the particular region in which statistics are to be predicted. The slant path attenuations at other elevation angles, 0 (0 -> 20ø), are arrived at using the csc 0 factor. The attenuation contribution of clouds which occur in the presence of rain is also considered using model liquid water content-height profiles. Eight comparisons of absolute probability fade distributions are made of the measured and predicted cases, namely, for Maryland (15 GHz), Texas (30 GHz), Slough, England (19 and 37 GHz), Fayetteville, N.C. (13 and 18 GHz), and Cambridge, Mass. (13 and 18 GHz). In comparing the measured and predicted cases, the overall average of the probability ratios was 1.4.