Estimating the root-zone soil moisture from the combined use of time series of surface soil moisture and SVAT modelling

This work investigates the possibility to retrieve the root-zone soil moist ure from the combined use of time series of surface soil moisture, that can be estimated from microwave remote sensing instruments, and Soil-Vegetatio n-Atmosphere-Transfer (SVAT) modeling. The analysis is based on the ISBA su rface scheme and two data sets acquired over soybean crops, in 1989 and 199 0. They include very detailed measurements of soil and vegetation character istics, mass and energy transfers in the soil-plant-atmosphere system and c rop remote sensing signatures in the thermal and microwave domains during a 2- or 3-month period. The 3-month experiment in 1989, made it possible to investigate the accuracy of the soil reservoir retrieval, as a function of the time period and repetitivity of the surface measurements included in th e retrieval process. This work contributes to a better definition of the re quirements for the use of remotely-sensed microwave observations of surface soil moisture. This is a crucial problem, if we consider the increasing po tential of microwave remote sensing technology and the fundamental needs in atmospheric and hydrological models for water transfer characterization in soil. (C) 1999 Elsevier Science Ltd. All rights reserved.