Contents 



Foreword iii 



Preface iv 



Chapter 1. The radio refractive index of air 1 



1.1. Introduction 1 



1.2. Dielectric constant of moist air 2 



1.3. Constants in the equation for A'^ 4 



1.4. Errors in the practical use of the equation for A^ 9 



1.5. Presentation of A^ data 13 



1.6. Conclusions 20 



1.7. References 21 



Chapter 2. Measuring the radio refractive index 23 



2.1. The measurement of the radio refractive index 23 



2.2. Indirect measurement of the radio refractive index 23 



2.3. Direct measurement of the refractive index 30 



2.4. Comparison between the direct and indirect methods of measure- 



ment 38 



2.5. Radiosonde lag constants 38 



2.5.1. Introduction 38 



2.5.2. Theory of sensor time lags 29 



2.5.3. Radiosonde profile analysis 41 



2.5.4. Conclusion 43 



2.6. References 45 



Chapter 3. Tropospheric refraction 49 



3.1. Introduction 49 



3.2. Limitations to radio ray tracing 52 



3.3. An approximation for high initial elevation angles 53 



3.4. The statistical method 54 



3.5. Schulkin's method 54 



3.6. Linear or effective earth's radius model 56 



3.7. Modified effective earth's radius model 59 



3.8. The exponential model 65 



3.9. The initial gradient correction method 77 



3.10. The departures-from-normal method 77 



3.11. A graphical method 80 



3.12. Derivations 1 82 



3.13. References 87 



Chapter 4, N climatology 89 



4.1. Introduction 89 



4.2. Radio-refractive-index climate near the ground 89 



4.2.1. Introduction 89 



4.2.2. Presentation of basic data 89 



4.2.3. Worldwide values of A^o 98 



4.2.4. Climatic classification by A^, 102 



4.2.5. Applications 105 



4.2.6. Critical appraisal of results 107 



4.2.7. Conclusions 108 



