Context and objectives
The moisture content and its vertical distribution (hereafter referred to as soil moisture profile) in the top meter of the soil is of critical importance in numerous hydrological, agricultural and meteorological processes. In order to make progress in our understanding of these processes (rainfall-runoff dynamics in catchments, crop water use during growing season, regional evapotranspiration, etc.) the need exists to develop new measurement techniques of the soil moisture profile. Recent advances in active microwave observations of the Earth’s surface provide great potential to develop such new measurement techniques, since it is well-known that the radar signal is affected by the surface soil moisture content. In this project we have focussed our attention on data assimilation schemes that allow to retrieve the moisture profile in the top meter of the soil from observations of the moisture content in the upper few centimetres of the profile. Such a data assimilation scheme combines infrequent surface soil moisture measurements with hydrological simulation models that propagate the measurements down in the profile. This technology will provide valuable information on soil moisture content over large areas, such as catchments, large irrigation perimeters and even whole regions.
Expected scientific results
- The laboratory experiment allowed us to establish the accuracy range of surface soil moisture estimation through active microwave observation of bare soil surfaces at about 5 % vol.
- A 1D data assimilation scheme to retrieve accurate soil moisture profile information from surface soil moisture measurements was developed.
- A sensitivity analysis resulted in the establishment of the accuracy range of soil moisture profile retrieval using infrequent and noisy data.
- We have shown for the first time that soil moisture profile retrieval is possible from measurements of the upper 5 cm of the soil.