Study On Combined Active/passive Microwave Remote Sensing Approach For Soil Moisture Retrieval With TRMM Data

Global energy and water cycle is a complex process. It is driven by a multiplicity of factors and the interactions between them, many of which are inadequately understood till now. Soil moisture is a key parameter in the global energy and water cycle. It will be of great improvement for land and atmosphere process research if we get high-accuracy and multi-scale soil moisture information. Microwave remote sensing is a very suitable instrument for soil moisture monitoring because of its sensitivity to the dielectric constant of soil which is dominated by soil moisture. However, microwave signal is also affected by surface roughness and vegetation cover of soil, which leads to many problems that should be solved in the soil moisture retrieval using microwave instruments.Researches show that radar is likely to be more sensitive to the surface feature such as surface roughness and plant structure and a passive microwave radiometer is likely to be more sensitive to the near surface soil moisture. On the other hand, for the spaceborne sensors, the spatial resolution of radar is always higher than that of radiometers. Therefore, researchers pay attention to how to do the soil moisture retrieval using a combined active/ passive microwave remote sensing instrument.The primary goal of this research is to develop a combined active/passive microwave remote sensing approach for soil moisture in Tibetan Plateau using PR and TMI onboard the TRMM satellite. The main contents of the study can be separated into three parts.Part I is the development of model.In the bare ground condition, we develop a soil moisture retrieval model against the parameters of PR and TMI, and then we build a numerical surface condition with the ground truth measurement of the study area in which we do the model test. For the vegetation cover ground, we do the surface scattering simulation using water-cloud model and MIMICS, and then do parameterization of the constructive species of the study area. Based on the parameterization, we confirmed the parameters of water-cloud model with the MIMICS simulation result. So we can do the vegetation cover soil moisture retrieval using the water-cloud model and the bare surface model above.