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.