Mid-infrared laser reflectance of moist soils

Area of Science:

• Earth and Environmental Sciences
• Physics
• Remote Sensing

Background:

• Soil moisture significantly influences soil properties and interactions with electromagnetic radiation.
• Understanding reflectance behavior across different spectral regions is crucial for remote sensing applications.

Purpose of the Study:

• To experimentally investigate the effect of varying moisture content on mid-infrared (9-11-µm) laser backscatter reflectance of soils.
• To differentiate and analyze the diffuse and coherent components of total reflectance.
• To develop and test an empirical model for diffuse reflectance based on physical mechanisms.

Main Methods:

• Experimental investigation of laser backscatter reflectance using mid-infrared lasers (9-11-µm).
• Separation of total reflectance into diffuse and coherent components.
• Analysis of reflectance changes with varying gravimetric moisture content across different soil types.

Main Results:

• Diffuse mid-infrared reflectance decreases with increasing gravimetric moisture content due to forward scattering and total internal reflection.
• Coherent reflectance initially increases with low moisture (reduced surface roughness), then decreases, and increases again near field capacity.
• An empirical model for diffuse reflectance was developed and validated against experimental data.

Conclusions:

• Laser reflectance in the mid-infrared is sensitive to near-surface soil moisture (approximately 0.25-mm depth).
• The findings suggest potential for using mid-infrared laser backscatter to monitor near-surface soil moisture.
• The study provides insights into the physical mechanisms governing soil-light interactions at different moisture levels.