170 N CLIMATOLOGY 



The average decrease of pressure, temperature, and humidity with 

 height produces a normal decrease of A'^. If, however, the temperature 

 increases with height, as in a temperature inversion, A^^ decreases more 

 rapidly and radio rays are superrefracted, dependent, of course, upon the 

 vapor pressure. Conversely, an unusually rapid decrease of temperature, 

 or an mcrease of humidity, with height produces a subnormal decrease of 

 A^ with height, or subrefraction of radio waves. In any event it is evident 

 from these figures that x4-profile effects on ray bending are most pro- 

 nounced at do = 0, are significantly less pronounced at do = 52 mrad 

 ('~3°), and continue to diminish with increasing do until, at ^o = 7r/2, 

 there is no bending at all and consequently all departures are zero. 



4.6.3. Conclusions 



The work of Schulkin and others has shown that characteristic total 

 bending differences in radio ray refraction exist between various air 

 masses. The present study extends Schulkin's conclusion by identifying 

 abnormal bending of radio rays with departures of refractive index struc- 

 ture from average in the lowermost layers of the air masses. Considera- 

 tion of departures of both ray bending and refractive index structure from 

 their value in a standard exponential atmosphere results in a suitable 

 method of cataloging air masses in terms of either refractive index struc- 

 ture or bending characteristics. 



4.7. References 



Resolution No. 71 (1948), Conf. of Directors, Internal. Meteorol. Organization 



(Lausanne, Switzerland). 

 World Atlas of Sea Surface Temperature Charts (1944), Hydrographic Office 



Publ. 225, chap. 4, No. 2. 

 Atlas of climatic charts of the oceans (1938), U.S. Weather Bureau Publ. 1247, 



Washington, D.C. 

 Johnson, W. E. (Nov.-Dec. 1953), An analogue computer for the solution of the 



radio refractive index equation, J. Res. NBS 51, No. 6, 335-342. 

 Gerson, N. C. (1948), Variations in the index of refraction of the atmosphere, 



Geofis. Pura Appl. 13, 3-4. 

 Bean, B. R. (Apr. 1953), The geographical and height distribution of the gradient 



of refractive index, Proc. IRE 41, No. 4, 549-550. 

 Misme, P. (Nov.-Dec. 1958), Essai de radioclimatologie d'altitude dans le nord 



de la France, Anna. Telecommun. 13, No. 11-12, 303-310. 

 Smithsonian Meteorological Tables (1951), Table 63, Sixth Revised Ed., Book 



(Washington, D.C). 

 Bean, B. R., and G. D. Thayer (1959), CRPL Exponential Reference Atmosphere, 



NBS Mono. 4. 

 Pickard, G. W., and H. T. Stetson (1959), Comparison of tropospheric reception, 



J. Atmos. Terrest. Phys. 1, 32-36. 

 Pickard, G. W., and H. T. Stetson (1950), Comparison of tropospheric reception 



at 44.1 Mc with 92.1 Mc over the 167-mile path of Alpine, New Jersey to 



Needham, Mass., Proc. IRE 38, No. 12, 1450. 



