Study On Soil Moisture Inversion And Application With Polarization Radar In Vegetated Area

The soil moisture content plays an essential role in predicting, estimating ard modeling major ecological processes such as evaporation, transpiration, surface runoff and ground water replenishment. Soil moisture deficit or surplus are often key facto rs affecting the temporal and spatial dynamics of vegetation systems. Thus, the information of temporal and spatial fluctuations of soil moisture content is relevant to a wide application fields, such as: the prediction of plant growth, determination of the proper time for sowing, the identification of agricultural areas with accelerated soil erosion and monitoring of dynamic soil processes acting on the surface (physical, chemical and biological). Furthermore, it serves as input parameters for hydrological and meteorological modeling and enables to identifying environmentally sensitive areas.Many studies showed that the backscattering coefficients of synthetic aperture radar (SAR) are very sensitive to surface soil moisture (or soil dielectric constants). Due to the complexity of land surface, the backscattering coefficients of Radar are also affected by surface roughness and vegetation canopy besides surface soil moisture, so it is difficult to estimate soil moisture under vegetation canopy. In recent years, many theoretical and experimental researches were done to understand the relationship between Radar backscattering and soil moisture, surface roughness and vegetation canopy. Based on L-band full polarization AirSAR data, this thesis tried to develop an algorithm to estimate soil moisture content under vegetation canopy.In this study we firstly build a simulated backscattering database in considering vegetation effect based on a first-order vegetation model, and then we decomposes the total backscattering signals into two components - the surface scattering components (the bare surface backscattering signals attenuated by vegetation canopy) and the sum of the direct volume scattering components and surface-volume interaction components at different polarizations. Without other ancillary data we at last eliminates the vegetation effects and estimates soil moisture content and it's change...