This study reviews recent progress on soil moisture data assimilation. Data assimilation is a process of merging observations with a system dynamic model to provide an improved estimate of the states of the environment. The application of data assimilation in hydrology is relatively new, however, rapid progress has been made in the last decade or so with the available remotely sensed soil moist...

Ground-reflected global positioning system signals measured by a geodetic-quality GPS system can be used to infer temporal changes in near-surface soil moisture for the area surrounding the antenna. This technique, known as GPS-interferometric reflectometry, analyzes changes in the interference pattern of the direct and reflected signals, which are recorded in signal-to-noise ratio (SNR) data, ...

Soil moisture products acquired from passive satellite missions have been widely applied in environmental processes. A primary challenge for the use of soil moisture products from passive sensors is their reliability. It is crucial to evaluate the reliability of those products before they can be routinely used at a global scale. In this paper, we evaluated the Soil Moisture Active/Passive (SMAP...

In situ soil moisture measurements are invaluable for calibrating and validating land surface models and satellite-based soil moisture retrievals. On a worldwide basis the number of meteorological networks measuring soil moisture is still limited and their data lack standardization of technique and protocol. In response to this, the International Soil Moisture Network (ISMN) was initiated to se...

Numerous land surface models exist for predicting water and energy fluxes in the terrestrial environment. These land surface models have different conceptualizations (i.e., process or physics based), together with structural differences in representing spatial variability, alternate empirical methods, mathematical formulations and computational approach. These inherent differences in modeling a...

The Soil Moisture and Ocean Salinity Mission (SMOS) acquires surface soil moisture data of global coverage every three days. Product validation for a range of climate and environmental conditions across continents is a crucial step. For this purpose, a soil moisture and soil temperature sensor network was established in the Skjern River Catchment, Denmark. The objectives of this article are to ...

Soil moisture is an important hydrologic state variable critical to successful hydroclimatic and environmental predictions. Soil moisture varies both in space and time because of spatio-temporal variations in precipitation, soil properties, topographic features, and vegetation characteristics. In recent years, airand space-borne remote sensing campaigns have successfully demonstrated the use of...

21 NASA's Soil Moisture Active Passive (SMAP) mission will carry the first combined spaceborne L-22 band radiometer and Synthetic Aperture Radar (SAR) system with the objective of mapping near-23 surface soil moisture and freeze/thaw state globally every 2-3 days. SMAP will provide three soil 24 moisture products; (i) high-resolution from radar (~3km), (ii) low-resolution from radiometer 25 (~3...