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Figure C-17. Percent of time gradient ^ -100 (N/km) : August 72 



Figure C-18. Percent of superrefractive layers thicker than 100 m : August 72 



Figure C-19. Percent of time gradient ^ -100 (N/km) : November 73 



Figure C-20. Percent of superrefractive layers thicker than 100 m: November 73 



Figure C-21. Percent of time gradient f= -157 (N/km) : February 74 



Figure C-22. Percent of ducting layers thicker than 100 m: February 74 



Figure C-23. Percent of time gradient ^ -157 (N/km) : May 75 



Figure C-24. Percent of ducting layers thicker than 100 m : May 75 



Figure C-25. Percent of time gradient ^ -157 (N/km) : August 76 



Figure C-26. Percent of ducting layers thicker than 100 m: August 76 



Figure C-27. Percent of time gradient ^ -157 (N/km) : November 77 



Figure C-28. Percent of ducting layers thicker than 100 m : November 77 



Figure C-29. Percent of time trapping frequency < 3000 Mc/s : February 78 



Figure C-30. Percent of time trapping frequency < 1000 Mc/s: February 78 



Figure C-31. Percent of time trapping frequency < 300 Mc/s : February 79 



Figure C-32. Percent of time trapping frequency < 3000 Mc/s : May 79 



Figure C-33. Percent of time trapping frequency < 1000 Mc/s: May 80 



Figure C-34. Percent of time trapping frequency < 300 Mc/s: May 80 



Figure C-35. Percent of time trapping frequency < 3000 Mc/s: August 81 



Figure C-36. Percent of time trapping frequency < 1000 Mc/s: August 81 



Figure C-37. Percent of time trapping frequency < 300 Mc/s : August 82 



Figure C-38. Percent of time trapping frequency < 3000 Mc/s : November 82 



Figure C-39. Percent of time trapping frequency < 1000 Mc/s: November 83 



Figure C-40. Percent of time trapping frequency < 300 Mc/s: November 83 



Figure C-41. Lapse rate of refractivity (N/km) exceeded 25 percent of time for 



100-m layer : February 84 



Figure C-42. Lapse rate of refractivity (N/km) exceeded 10 percent of time for 



100-m layer: February 84 



Figure C-43. Lapse rate of refractivity (N/km) exceeded 5 percent of time for 



100-m layer: February 85 



Figure C-44. Lapse rate of refractivity (N/km) exceeded 2 percent of time for 



100-m layer: February 85 



Figure C-45. Lapse rate of refractivity (N/km) exceeded 25 percent of time for 



100-m layer: May 86 



Figure C-46. Lapse rate of refractivity (N/km) exceeded 10 percent of time for 



100-m layer: May 86 



Figure C-47. Lapse rate of refractivity (N/km) exceeded 5 percent of time for 



100-m layer: May 87 



Figure C-48. Lapse rate of refractivity (N/km) exceeded 2 percent of time for 



100-m layer: May 87 



Figure C-49. Lapse rate of refractivity (N/km) exceeded 25 percent of time for 



100-m layer : August 88 



Figure C-50. Lapse rate of refractivity (N/km) exceeded 10 percent of time for 



100-m layer : August 88 



Figure C-51. Lapse rate of refractivity (N/km) exceeded 5 percent of time for 



100-m layer : August 89 



Figure C-52. Lapse rate of refractivity (JV/km) exceeded 2 percent of time for 



100-m layer: August 89 



Figure C-53. Lapse rate of refractivity (N/km) exceeded 25 percent of time for 



100-m layer : November 90 



Figure C-54. Lapse rate of refractivity (N/km) exceeded 10 percent of time for 



100-m layer : November 90 



Figure C-55. Lapse rate of refractivity (N/km) exceeded 5 percent of time for 



100-m layer : November 91 



Figure C-56. Lapse rate of refractivity (N/km) exceeded 2 percent of time for 



100-m layer: November 91 



Table C-l. Median and minimum trapping frequency (Mc/s) of ducting layers 92 



Figure C-57. (a) Cumulative probability distributions of dN/dh for ground-based 



100-m layer: Aden, Arabia (February, May) 93 



Figure C-57. (b) Cumulative probability distributions of dN/dh for ground-based 



100-m layer : Aden, Arabia (August, November) 94 



vii 



