hour rain are plotted. It is seen tliat tlie numerous 

 smaller drops hardly contribute to the attenuation, 

 which is caused mostly liy the fewer larger drops and 

 has a maximum around the •2.5-nim drops. 



In Table 9 is given the total attenuation (decibels 

 per kilometer) in the wavelength range 1.25 to 100 

 cm in different rains of precipitation rates ranging 

 from 3.46 to 43.1 mm per hour cori'esponding to 

 given distributions. In Figure 11 are plotted some 

 curves showing, for a few rains, the variation of the 

 total attenuation factor as a function of the wave- 

 length. The dashed portions of these curves join the 



40 50 60 70 

 AIN CM 



80 90 100 



Figure 11. Attenuation in rains of known drop size 

 distribution as a function of the wavelength. The 

 abscissa gives the wavelength, X, in centimeters. The 

 ordinate scale gives logio a, where the attenuation con- 

 stant, a, is expressed in decibels per kilometer. The 

 letters on the curves refer to the drop size distributions 

 given in Table 7. 



40 



45 



5 10 15 20 25 30 35 



PRECIPITATION RATE IN MM PER HR 



Figure 12. (1) Computed K-band attenuation based 

 on experimental drop size distributions. (2) Theoretical 

 upper limit. a/;) = 0.16 db/km/mm/hr. i=18 C. 



points previously computed/- the calculations start- 

 ing at A = 5 cm. 



Figures 13. 13, and 11 represent, at three typical 

 wavelengths, the total attenuations in different rains. 

 The results of the calculation are represented by the 

 points indicated on these figures, and the smooth curve 

 passing through tliese points serves to illustrate the 



1.2 



o 0.8 



0.6 



«» 0.4 



0.2 



2 y/ 



jX Q^ 



10 15 20 25 30 35 



PRECIPITATION RATE IN MM PER HR 



45 



Figure 13. (1) Computed X-band attenuation based 

 on experimental droiJ size distributions. (2) Theoretical 

 upper Umit. a/^ = 0.045 db/km/mm/lir. (= IS C 



