GROUND-BASED ATMOSPHERIC DUCTS 



141 



O 



c 



CD 

 U 



\_ 



cu 

 CL 







M A 



M 



N D 



Months of the Year 



Figure 4.36. Frequency of occurrence of ground-based ducts. 



by assuming a linear decrease of n within the duct. The coefficient c 

 is a constant and 7 is a function of the n gradient excess over the minimum 

 value of An/A/i = 1/a. Expressing X^ai in centimeters, and d in meters, 

 then 



{Kl^ _ 0.157) 10;' 



(4.25) 



