Contents 



Page 



Preface m 



Abstract 1X 



1. Introduction 1 



2. Discussion of Basic Data 2 



3. World Maps of N(z) 4 



3.1. Development 4 



Figure 1. Three-part exponential fit to mean N-profile: Koror. 5 



Figure 2. Three-part exponential fit to mean N-profile : Dakar 6 



3.2. Discussion of N(z) Map Contours 4 



3.3. Reliability of Contours of N(z) Maps 6 



3.4. Problem Areas of N(z) Maps 7 



Figure 3. Five-year mean wet refractivity term: February 8 



Figure 4. Five-year mean wet refractivity term : May 9 



4. World Maps of AN 10 



4.1. Development _ LL _ L 10 



4.2. Discussion of Contours and Reliability of AN Maps 10 



5. World Maps of Extreme N-Gradients 12 



5.1. Development 12 



5.2. Discussion of Gradient Map Contours (Subrefraction) 12 



5.3. Discussion of Gradient Map Contours (Superrefraction and Ducting) 14 



5.4. Discussion of Cumulative Distributions of Ground-Based Gradients 15 



Figure 5. Five-year mean vertical refractive gradient profile: Aden 16 



Figure 6. Five-year mean vertical refractive gradient profile: Nicosia 17 



5.5. Reliability and Limitations of Ground-Based Refractivity Gradient Data 17 



6. World Maps of Mean Tropopause Altitudes 19 



7. Appraisal of Results 20 



7.1. Accuracy of N(z) Maps 20 



Table 1. Standard errors of 5-year mean values of monthly mean A' s for 40 stations 20 



Figure 7. Correlation of AN: monthly mean A T -profiles versus monthly mean exponential model 21 



Table 2. Absolute errors in recovering mean A T from map contours for 32 stations 21 



Table 3. Approximate total standard errors, <r T , for N(z) maps in appendix A 22 



7.2 Accuracy of AN Maps. 23 



Figure 8. Correlation of AN: monthly mean N-profiles versus monthly mean weather 



summary data 22 



7.3. Accuracy of Gradient Maps 24 



8. Conclusions 25 



9. References 26 



10. Appendix A. World Maps of N(z) Parameters 29 



Table A-l. Cumulative distribution levels of surface refractivity 30 



Figure A-l. Location of N(z) data stations 32 



Figure A-2. Mean sea-level dry term, D„ : February 33 



Figure A-3. Mean sea-level wet term, W : February 33 



Figure A-4. Dry-term tropospheric scale height in km, Hi : February 34 



Figure A-5. Dry-term stratospheric scale height in km, H« : February 34 



Figure A-6. Wet-term scale height in km, H w : February 35 



Figure A-7. Mean density tropopause altitude in km, z t : February 35 



Figure A-8. Mean sea-level dry term, Do : May 36 



Figure A-9. Mean sea-level wet term, W a : May 36 



Figure A-10. Dry-term tropospheric scale height in km, Hi : May 37 



Figure A-ll. Dry-term stratospheric scale height in km, H 2 : May 37 



Figure A-12. Wet-term scale height in km, H w : May 38 



Figure A-13. Mean density tropopause altitude in km, z t : May 38 



Figure A-14. Mean sea-level dry term, £>„: August 39 



