Infrared transmission through cirrus clouds: a radiative model for target detection

Area of Science:

• Atmospheric optics
• Remote sensing
• Radiative transfer

Background:

• Cirrus clouds composed of hexagonal ice crystals significantly impact infrared (IR) transmission.
• Accurate modeling of IR transmission through cirrus clouds is crucial for effective target detection systems.
• Existing models often lack detailed parameterization of ice crystal properties and multiple scattering effects.

Purpose of the Study:

• To develop an IR transmission model for thin and subvisual cirrus clouds specifically for target detection applications.
• To parameterize ice crystal size distribution and cloud position based on ambient temperature.
• To compute scattering and absorption properties of hexagonal ice crystals for transmission calculations.

Main Methods:

• Developed parameterized equations for single scattering properties of hexagonal column and plate crystals using geometric ray-tracing.
• Employed a successive order-of-scattering approach to model multiple scattering effects.
• Computed direct radiance, path radiance, and background radiation at 3.7- and 10-micrometer wavelengths.

Main Results:

• Demonstrated that background radiance at 3.7-micrometers is minimal, enabling high contrast for target detection.
• Showcased the model's ability to efficiently evaluate IR transmission through cirrus clouds.
• Validated the effectiveness of the 3.7-micrometer wavelength for detecting airborne and ground-based objects.

Conclusions:

• The developed IR transmission model accurately simulates radiation transfer through cirrus clouds.
• The 3.7-micrometer wavelength is optimal for target detection in the presence of thin cirrus clouds.
• The model provides a valuable tool for enhancing the performance of remote sensing and target detection systems.