A radar-radiometer soil moisture estimation framework with adaptive regularization and join physics

A unified framework for surface soil moisture estimation is presented in this work wherein both radar backscatter and radiometer brightness temperature measurements are effectively and simultaneously utilized. Within this combined estimation approach a regularization parameter is also introduced enabling the algorithm to perform radar-only, radiometer-only or joint radar-radiometer soil moisture retrieval when necessary. Through the use of numerical simulations, as well as field campaign data, the practicality and applicability of this new technique will be highlighted and two key features will be presented and discussed: (1) improved soil moisture estimation in a joint radarradiometer framework (2) further reduction of estimation errors by utilizing the underlying physical relationships between emission and scattering. The latter exploits the joint physics of two measurement modalities within the retrial process.