ABSORPTION ESTIMATE FOR OTHER AREAS 



289 



squares to obtain the total path absorption as a linear function of the 

 absolute humidity. The parameter is a statistical regression line at each 

 frequency for path propagation distances of 100, 300, and 1,000 km as 

 given in table 7.5, and also plotted on figure 7.14, allowing the reader to 

 estimate the regression line for frequencies other than those of the 

 present study [3]. 



Statistics for the variation of absolute humidity have already been 

 given, and contours of the mean values of absolute humidity for the world 

 are given on figures 7.15 and 7.16 for the months of February and August 

 respectively. It is noted that the absolute humidity for either month is 

 greater in the coastal regions than in the continental interiors and that 

 the windward sides of continents have larger values than do the leeward 

 sides. 



By reference to figures 7.15 and 7.16 [16] for the United States, and 

 figure 7.14, estimates of radio power loss due to absorption may be 

 obtained. As an example, figure 7.17 gives the values expected to be 

 exceeded 1 percent of the time over a 300 km propagation path at 10,000 

 Mc/s for the United States during the month of August. 



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Figure 7.15. Average absolute humidity (g/ni^), February. 



