430 SUBJECT INDEX 



Seasonal range 



of field strength, 174 



of No {see also Climatology), 111-121, 129-130 

 Shadow zones, 148-150, 152-155, 157, 159-160 

 Slant range, 335, 360 

 Snell's law in polar co-ordinates, 49, 84-87, 136-137, 165, 326 



derivation, 84-87 

 Snow attenuation, 302 



Space cross sections of refractive index, 211-217, 221 

 Sprung's formula, 12 

 Stability 



atmospheric, 238-241, 258, 260, 262-263, 266 



thermal (see Thermal stability) 

 Standard atmosphere, 9, 11, 16-17, 64, 92-93, 180, 186, 312-314 

 Statistical method of computing refraction, 54, 335, 342-350, 379-380, 382-384 

 Stratopause, appoximate location, 313 

 Stratosphere 



approximate extent, 313 



meteorological characteristics of, 313 

 Subrefraction, 133, 248-249, 329, 332-333 

 Subsidence, relative to duct formation, 133-135, 180, 182, 185 

 Superior air mass, 79, 169 

 Superrefraction {see also Ducting), 133-135, 146-148, 156, 169, 182, 248, 250, 328-329, 



332-333 

 Surface duct (see Ground-based radio ducts) 

 Synoptic illustration of A'' change (see Frontal zone) 



T 



Temperature dependence 



of gaseous absorption (see Van Vleck's absorption formulas) 



of refractivity, 1-8 

 Thermal noise temperature, 304-307 



definition, 305 

 Thermal stability, 239-241, 262, 265 

 Tilted elevated layer, 249-251 



Time cross sections of refractive index, 213, 217-221 

 Tracking system, radio, 334 

 Transhorizon propagation mechanisms, 248 

 Transition zone (see Frontal zone) 

 Trapping of a radio ray (see Ducting) 

 Tropopause, approximate location, 313 

 Troposphere 



approximate extent, 313 



meteorological characteristics of, 313 

 Turbulence 



atmospheric, 260 



parameter (see Pi-factors) 



U 



Unstratified layer, 248, 250-251 



Van Vleck's absorption formulas, 270, 272-275 



Velocity of radio propagation, 56 



Vertical 



gradient of A^ (see Refractivity) 



profile of A'^ (see Refractivity) 



ray, 329 

 Vetter refractometer, 31, 34-35 



W 



Warm front (see Frontal zone) 

 Water vapor 



absorption properties of (see Attenuation by gases) 



an average refractivity value of, 9 



density (see absolute humidity) 



dependence of refractivity, 1-8 



