FREQUENCY OF OCCURRENCE OF RAIN ATTENUATION OF 10 DB OR GREATER AT 10 GC
Final rept. on phases 1 and 2
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
Pagination or Media Count:
An analysis of quantitative radar data supplemented by records of hourly precipitation amounts and excessive short duration rainfall at selected points was made to determine the frequency of occurrence of severe attenuation defined here as 10 db or more of 10 Gc radiation by rain at stations in central New England. The study was based on two years data. It was found that at an elevation of 5 degrees above the horizon severe attenuation by intense thunderstorms may be expected for approximately 32 hours per year if all directions of propagation are involved. Along a particular azimuth it occurs for 5 hours per year. At an elevation angle of 10 degrees the times are 14 and 3 hours respectively at 20 degrees they are 3-12 and 1-13 hours. Coarse resolution of the radar data precluded analysis at higher elevation angles. Severe attenuation by heavy widespread rain is considerably more probable in southeastern New England, where approximately 4 hours per year at 5 degrees elevation may be expected, than farther to the north and west. This type of storm does not cause as much as 10 db of attenuation at an elevation of 10 degrees or more. Techniques are suggested for applying the results to regions where rain gauge records but no quantitative radar data are available. Results of this preliminary analysis cannot be extended to higher radiation frequencies or smaller amounts of attenuation, because less intense storms whose statistics have not yet been thoroughly explored would be involved. An investigation of all types of New England storms, their intensities, their frequency of occurrence and the attenuation they would cause is in progress.
- Radiofrequency Wave Propagation