Advances in the use of Distributed Temperature Sensing for measuring soil moisture

This presentation will focus on advances in the use of passive distributed temperature sensing for large-scale, high resolution monitoring of soil moisture. In this approach, cables are plowed into the ground at several depths and use to make continuous measurements of soil temperature. Unlike Active DTS, external heating is not applied to the cables. The soil temperature profile variations in response to the diurnal net radiation cycle are observed instead. Recent results will be presented from an improved inversion approach, in which the vertical profile of thermal diffusivity is inferred from the cable temperatures and limited ancillary information. Results will also be presented from a promising new data assimilation approach, in which temperature observations are assimilated into a model to obtain simultaneous soil moisture and temperature profiles. This approach is particularly well suited to handling the vertical and horizontal spatial variability in moisture content and soil texture. It is less sensitive to errors in cable depth than the inversion method and circumvents the problem of inferring one of two possible soil moisture values from a thermal diffusivity estimate. We will conclude with some perspectives on how this approach can be extended to facilitate the combined use of active and passive DTS for soil moisture estimation.