ATTENUATION BY RAIN 



295 



similar to table 7.8 an additional set of results is contained for rains of 

 measured drop size distribution. 



Since the total attenuation cross section [26] depends on the temperature 

 (because of its effects on the dielectric properties of water), it is important 

 to evaluate the attenuation of rains whose drops are at different tempera- 

 tures from those in the preceding tables. Table 7.10 contains the neces- 

 sary data relative to the change of attenuation with temperature and is 

 to be used with table 7.8. For example, in table 7.8, with a p^fcipitation 

 rate of p = 0.25 mm/hr, temperature of 18 °C, X = 1.25 cm, the attenua- 

 tion is 0.0215 dB/km. Using the correction factors obtained from table 

 7.10, for the same general conditions of precipitation and wavelength, 

 for a temperature reading of °C, the attenuation reads 0.02043 dB/km; 

 for a value of 30 °C an attenuation of 0.019350 dB/km is noted; and for 

 a temperature of 40 °C the attenuation is 0.01742 dB/km. 



6.0 



5.0 



a 3.5 



2.0 2.5 3.0 3.5 4.0 5.0 6.0 7.0 8.0 10 



TRANSMISSION LOSS IN DECIBELS PER MILE 



Figure 7.20. Transmission loss in decibels per mile versus rainfall in inches per hour. 

 (After Hathaway and Evans, 1959). 



