Remote Determination of Soil Moisture and Evapotranspiration from ThermalInfrared Measurements: Detection of a Drying Threshold

摘要

Important objectives in the work were to (1) model the water movement through thesoil/plant/atmosphere system and (2) to use, in conjunction with this model, remote measurements of infrared surface temperature and vegetation index to calculate soil water content and (3) determine whether water stress can be detected radiometrically over vegetation, specifically to identify the threshold at which these measurements for remotely estimating soil water content over both bare soil and vegetation, and to specify the limits of accuracy in the soil water content estimates. Much of the modeling efforts have been devoted to improving the vegetation component of the model. Sensitivity tests with the vegetation model suggest that water stress in vegetation may be detectable for a period of a few days prior to wilting, provided that the atmospheric demand is large, an appropriate threshold leaf water potential exists and plant storage capacity is not large. Horizontal variations in radiometric surface temperature over sparse vegetation may simply reflect horizontal variations in canopy density rather than horizontal variations in soil water content.