Abstract
The aim of this paper is to propose a methodology combing multi-temporal X-band SAR images (TerraSAR-X) with continuous ground thetaprobe measurements, for the retrieval of surface soil moisture and texture at a high spatial resolution. Our analysis is based on seven radar images acquired at a 36° incidence angle in the HH polarization, over a semi-arid site in Tunisia (North Africa). The soil moisture estimations are based on an empirical change detection approach using TerraSAR-X data and ground auxiliary thetaprobe network measurements. Two assumptions were tested: (1) roughness variations during the three-month radar acquisition campaigns were not accounted for; (2) a simple correction for temporal variations in roughness was included. The results reveal a small improvement in the estimation of soil moisture when a correction for temporal variations in roughness is introduced. By considering the estimated temporal dynamics of soil moisture, a methodology is proposed for the retrieval of clay and sand content (expressed as percentages) in soil. Two empirical relationships were established between the mean moisture values retrieved from the seven acquired radar images and the two soil texture components over 36 test fields. Validation of the proposed approach was carried out over a second set of 34 fields, showing that highly accurate clay estimations can be achieved. Maps of soil moisture, clay and sand percentages at the studied site are derived.
Highlights
Physical soil parameters play an essential role in the functioning of the continental water cycle.Soil moisture is a key parameter that can be used for multi-domain applications, hydrology and agronomy in particular
The aim of this paper is to demonstrate that it is possible to retrieve both of these soil parameters from the same experimental campaign, using a single radar signal configuration
The present paper proposes an empirical algorithm based on the use of high-resolution radar TerraSAR-X
Summary
Physical soil parameters play an essential role in the functioning of the continental water cycle.Soil moisture is a key parameter that can be used for multi-domain applications, hydrology and agronomy in particular. In the case of semi-arid and arid regions, this parameter is important for water resources and irrigation management decisions, understanding land surface processes, and estimating runoff and soil erosion potential [1]. The temporal variability of soil water properties can arise from factors such as texture, tillage, cropping and other management practices. These can adversely affect yield and complicate irrigation scheduling [3,4]. The variability of a soil’s texture, its clay content in particular, has a significant influence on its spatial moisture distribution and can lead to difficulties when interpreting soil moisture measurements recorded over large areas for the purposes of irrigation scheduling decisions
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