Nominal SVP (Sound Velocity Profile)

4850ft/s 4900 ft/s 4950 ft/s 5000ft/s

Speed of Sound

300 600

3000

6000

9000

Surface Layer

Seasonal Thermocline

Main Thermocline

Deep Isothermal Layer

winter

“Layer”

Typical SVP

Gradients and Bending

c

z

c

c

z

z

Iso-speed

positive

negative

Surface Duct – Surface Shadow Zone

SVP

SVP

positive

negative

Surface Shadow Zone Implications

Originally called the “afternoon effect”

Convergence Zone

Depth Excess > 300 fathoms

CZ Effect on Transmission Loss (TL)

TL (dB)

Deep Shadow Zones

BD = 17(LD)1/2 if LD < 60m.BD = 17(LD)1/2 if LD < 60m.BD = LD + 60m if LD > 60m.BD = LD + 60m if LD > 60m.

Deep sound channelSound speed

dept

h

range

Mixed Layer Example

• 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

D = 40 mL = 100 mC1 = 1500 m/sg = 0.017 s-1

S

Mixed Layer

Summary

Positive gradient, g

z1

z2

x1 x2

c1

c2

1

2

R

1 1x x R sin sin

1 1z z R cos cos

1

1

cR

g cos

1

1

cos cos

c c

1

1

c c cg

z z z