A PRELIMINARY MICROWAVE ATTENUATION CLIMATOLOGY FOR THE MONTREAL AREA BASED ON WEATHER RADAR DATA.
MCGILL UNIV MONTREAL (QUEBEC) STORMY WEATHER GROUP
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Radar records of thunderstorms for a five-month period including thhe summer of 1963 were analyzed statistically to determine frequencies of occurrence of high attenuations over propagation paths in various directions. Results are given in graphs of the number of hours per season that certain attenuations are exceeded for 100-mi horizontal propagation paths and for radio frequencies ranging between 5.5 and 45 GHz. On the assumption that storm structure is uniform up to a height of 5 mi, above which no attenuation occurs, the results are expressed for slant paths with elevations up to 20 degrees. It was found that the statistics for the high attenuations considered 10 db and greater at 10 GHz are essentially determined by rainfall rates of 25 mmhr and greater, and are rather insensitive to the assumed form of the relationship between rainfall rate and attentuation. A significant dependence on the bearing of the propagation path is evident. An assumption about the translation velocity of storms enabled the computation of the expected number of severe attenuation occurrences in a summer season. Author