Modeling the turbulent trailing ship wake in the infrared.

Area of Science:

• Remote Sensing
• Fluid Dynamics
• Oceanography

Background:

• Ship wakes create detectable infrared signatures due to altered sea surface temperature and roughness.
• Existing methods lack detailed modeling of the turbulent wake's infrared properties.

Purpose of the Study:

• To develop a phenomenological model for the infrared radiance of a ship's turbulent trailing wake.
• To correlate sea surface roughness variations with turbulent intensity within the wake.

Main Methods:

• Utilized the Cox and Munk probability distribution function to describe sea surface slopes.
• Differentiated wake and background sea surfaces by the variance of sea surface slopes.
• Calculated reflected and emitted infrared radiances considering solar, atmospheric, and sky inputs.

Main Results:

• The model predicts infrared contrast based on sea surface slope variance and turbulent intensity.
• Calculated wake radiance shows strong dependence on observer zenith angle.
• Model predictions align well with trends observed in airborne infrared imagery.

Conclusions:

• The developed model accurately represents the infrared contrast of ship wakes.
• Observer angle significantly influences the detectability and nature (positive/negative contrast) of ship wakes in infrared.
• The model provides a valuable tool for analyzing and predicting ship wake signatures.