332 



REFRACTION AND REFRACTIVE INDEX MODELS 





LJ 



O 



_J 



3 







40 



240 



320 



360 



DISTANCE IN KILOMETERS 

 Figure 8.15. Ca-pe Kennedy, to 10 km, altitude of ray versiis distance. 



months are reported. Therefore, because one of the more extreme cases 

 is represented by the November 5 example, one might conclude that much 

 less than 20 percent of the observations would show the same degree of 

 horizontal n change as the profile studied. 



If one further hypothesizes that the greatest horizontal n change would 

 be associated with ducting conditions, then the percentage incidence of 

 ducts as evaluated from radiosonde observations, listed for various 

 stations in table 8.3 would indicate that the effects of horizontal changes 

 of n sufficient to cause variations in the ray path as large as those of the 

 present study would be observed less than 15 percent of the time, regard- 

 less of geographic location. 



The probable importance of subrefractive layers upon the prediction 

 of refraction effects has emerged as a secondary result of the present study. 

 Although subrefraction is normally neglected, it is potentially a very im- 

 portant refractive factor for distances of, say, less than 40 km. Even 

 though the percentage occurrence of subrefractive layers can be as large 

 as 6 percent (see table 8.4), this effect is frequently offset by the con- 

 current occurrence of an adjacent superrefractive layer, as is illustrated 

 by the Cape Kennedy example. 



