Nominal SVP (Sound Velocity Profile)

1. winter Speed of Sound 4850ft/s 4900 ft/s 4950 ft/s 5000ft/s Surface Layer 300 600 3000 6000 9000 Seasonal Thermocline Main Thermocline Deep Isothermal Layer Nominal SVP (Sound Velocity Profile) “Layer”

2. Typical SVP

3. c  z  c  z  c z  Gradients and Bending Iso-speed positive negative

4. Surface Duct – Surface Shadow Zone SVP positive SVP negative

5. Surface Shadow Zone Implications Originally called the “afternoon effect”

6. Convergence Zone Depth Excess > 300 fathoms

7. CZ Effect on Transmission Loss (TL) TL (dB)

8. Deep Shadow Zones • BD = 17(LD)1/2 if LD < 60m. • BD = LD + 60m if LD > 60m.

9. Deep sound channel range Sound speed depth

10. Mixed Layer Example D = 40 m L = 100 m C1 = 1500 m/s g = 0.017 s-1 • Find sound speed at S and at bottom of layer • Angle of the rays at the source • Angle of the rays at the surface • Radius of curvature of the ray • Skip distance , X S

11. Mixed Layer

12. x2 x1 R c1 z1 q1 z2 c2 q2 Positive gradient, g Summary