Environmental Variability

Temperature changes

• Note the variation in temperature across the hours of the day, and across days.

• Gradient of temperature between 30m and 50m.

• Sept. 21: three measurements

  • note how warming of surface temperature increases temperature of water with the thermocline that moves deeper and becomes steeper
  • note the presence of a surface duct in the first measurement at 06:53h. Warmer water is at 2m depth: in the morning the water is warmer at 2m depth.

• Sept. 22: similar behaviour to that of Sept 21 but at 10:25h thermocline is higher.

• Note that different environments means different acoustic performance!

• From Sept 22 to Sept 28 bad weather and water mixing (not completely) which meant cooler water in the first part of the water column and less steep gradients.

Time-varying thermocline

Tranmission Loss - Source depth constant, SSP change

Figure from John Potter, ACommsNet13.

Source depth variation

Tranmission Loss - source depth change, SSP constant.

Figure from John Potter, ACommsNet13.

• Geometry and environmental variations are key to characterise acoustic propagation, even in the same geographical location!