Soil moisture retrieval from remote sensing

Soil moisture is an important part in land ecohydrological cycle, therefore it is of great significance to acquire soil moisture data timely and accurately in the study of global climate problems, in construction of watershed hydrological models and in monitoring droughts. Development of remote sensing techniques in the last few decades has enabled efficient methods to be developed to retrieve soil moisture parameter. Here, developments of visible-near infrared, thermal infrared, visible-near-thermal infrared, active microwave and passive microwave remote sensing, and corresponding soil moisture inversions are reviewed. GNSS-R technology combined with active and passive microwave remote sensing is discussed. Major works of remote sensing inversion of soil moisture are generalized, development trend of soil moisture remote sensing retrieval is summarized.