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Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data

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Reflectance and albedo differences between wet and dry surfaces.

S A Twomey¹, C F Bohren, J L Mergenthaler

¹University of Arizona, Institute of Atmospheric Physics, Tucson, Arizona 85721, USA.

|February 1, 1986

Summary

Natural media like sand darken when wet due to decreased refractive index, increasing light scattering and absorption. This phenomenon has implications for remote sensing applications.

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Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

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Area of Science:

Optics
Materials Science
Geophysics

Background:

Natural materials like sand and soil appear darker when wet.
This darkening is attributed to changes in the optical properties of the medium surrounding particles.

Purpose of the Study:

To investigate the optical phenomenon of darkening in wet natural media.
To validate a theoretical model explaining the observed reflectance changes.
To explore the implications for remote sensing.

Main Methods:

Experimental measurement of sand reflectance with various wetting liquids.
Comparison of experimental data with a simple scattering theory.

Main Results:

Measurements showed good agreement with the simple theory predicting darkening.
The refractive index change significantly influences scattering and absorption.

Conclusions:

The darkening of wet natural media is primarily due to decreased particle-medium refractive index.
The findings support the proposed theoretical explanation.
Observed reflectance differences between wet and dry surfaces are relevant for remote sensing.