Laboratory-Based Rainfall Effects on LWIR Soil Reflectance

The long-wave infrared reflectance of in situ disturbed and undisturbed soils will often have distinct spectral characteristics that are dependent on the soil's physical and spectral constitutive properties. This study examines how rainfall alters the measured directional-hemispherical thermal infrared (8-14 μm) spectral reflectance of a disturbed soil with a specified sand/silt ratio using a calibrated rainfall simulator. For an accumulated rainfall of 8.0 cm, the mean disturbed soil thermal infrared spectral reflectance within 8.1-9.2-μm waveband increases from an initial reflectance of 13% to a maximum reflectance of 31 %. Sixty percent of this reflectance change occurred with only 1.0-cm accumulated rainfall. This study shows that, for this described disturbed sand/silt soil mixture, small accumulated rainfall amounts significantly alter the directional-hemispherical thermal infrared spectral reflectance.