266 TRANSHORIZON PARAMETERS 



One might well wonder why the correlations of Qe and field strengths 

 yield a higher correlation relative to that with AA'^ or A^s on a monthly 

 median basis than on a daily basis. This is apparently due to the non- 

 linear nature of the averaging process of g e which is dependent upon the 

 nonlinear weighting of the N{h) profile inherent in the refraction process. 

 On the other hand, the average AA'^ or A^^^ obtained from the average N{h) 

 curve is the same as that obtained from averaging AA'' or N s. Correla- 

 tions on n and field strength on a monthly median basis are now under 

 study. 



6.3.6. Conclusions 



In conclusion, we reach the opinion that the results of previous experi- 

 ence with the dependence of radio refraction upon N s and the concept 

 of stability are incorporated into IT. The resultant correlation with 

 radio data on a 3-hourly median basis is perhaps the most encouraging 

 obtained to date, but still, appears to be a marginal improvement over 

 the time-honored, and much simpler, parameter AA'^. This conclusion 

 could well change with broader experience on other paths and radio 

 frequencies. 



6.4. References 



[1] Bean, B. R., and F. M. Meaney (Oct. 1955), Some applications of the monthly 



median refractivity gradient in tropospheric propagation, Proc. IRE 43, No. 



10, 1419-1431. 

 [2] Bean, B. R., and B. A. Cahoon (Jan.-Feb. 1961), Correlation of monthly median 



transmission loss and refractive index profile characteristics, J. Res. NBS 65D 



(Radio Prop.), No. 1, 67-74. 

 [3] Misme, P. (Mar .-Apr. 1960), Le gradient equivalent mesure direct et calcul 



theorique, Ann. Telecommun. 15, No. 3-4, 93. 

 [4] Misme, P. (Nov.-Dec. 1960), Quelques aspects de la radio-climatologie, Ann. 



Telecommun. 15, No. 11-12, 266. 

 [5] Misme, P. (Jan.-Feb. 1961), Essais de radio climatologie dans le bassin du 



Congo, Ann. Telecommun. 16, No. 1-2, 29. 

 [6] Flavell, R. G., and J. A. Lane (Jan. 1963), The application of potential refractive 



index in tropospheric wave propagation, J. Atmos. Terrest. Phys. 24, 47-50. 

 [7] Moler, W. F., and W. A. Arvola (Aug. 1956), Vertical motion in the atmosphere 



and its effect on VHF radio signal strength, Trans. Am. Geophys. Union 37, 



399-409. 

 [8] Moler, W. F., and D. B. Holden (Jan.-Feb. 1960), Tropospheric scatter propaga- 

 tion and atmospheric circulations, J. Res. NBS 64D (Radio Prop.), No. 1, 81-93. 

 [9] Rice, P. L., A. Longley, and K. A. Norton (1959), Prediction of the cumulative 



distribution with time of ground wave and tropospheric wave transmission 



loss. Part I, NBS Tech. Note 15. 

 [10] Pickard, G. W., and H. T. Stetson (Jan. 1950), Comparison of tropospheric 



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

 [11] Bonavoglia, L. (Dec. 1958), Correlazione fra fenomeni meteorologici e propa- 



gazione altre I'orizzonte sul Mediterraneo, Alta Frequenza 27, 815. 



