| Soil moisture, that is, soil moisture or soil water content, is an important parameter in the field of hydrology, meteorology, soil science, ecology, and agricultural sciences. Soil moisture determines the surface transpiration, affects the demand for water resources of humans and farming, and plays an important role in the global water cycle. Because Soil moisture play an important role in the earth sciences research, So a large-scale and high efficiency measurement is needed in process of soil moisture measurement.Remote sensing can meet the need of large-scale soil moisture monitoring by different bands retrieval. Microwave Remote Sensing is of the advantages to all-day, multi-polarization, high-resolution, penetrating, and the sensitivity of moisture content. And it is a very effective means of monitoring soil moisture. The physical basis of microwave remote sensing to monitor soil moisture is dielectric characteristics of the soil having closely related with its water content. Passive Microwave monitoring soil moisture, mainly depend on the use of microwave radiation measuring the microwave emission by soil or brightness temperature. The AMSR/E passive microwave radiometer onboard the Aqua satellite, provides a physical platform of much accurate monitoring of soil moisture.In passive microwave remote sensing, radiation signal changes with the impact of the soil dielectric constant. Soil moisture is a key parameter to determine the soil dielectric constant. Based on soil dielectric properties and soil dielectric constant model, the relationship of the soil surface brightness temperature and soil moisture is established. In this study, Dobson model, a soil dielectric constant model, is used to establish the relationship between soil dielectric constant and soil moisture. By inputting some specific parameters, such as frequency, moisture and soil texture (such as sand, clay content), and surface temperature, the real and imaginary parts of soil dielectric constant can be gotten by Dobson model. Thereby the relationship between soil dielectric constant and the soil moisture content is achieved.In the study of soil moisture retrieval, the geometric roughness of the soil surface is an important factor to effect the changes of soil emissivity. Changes in the surface roughness of the surface have a great effect on the soil emissivity. In present study, Q/H model is a semi-empirical model used to describe the changes of rough surface.Surface brightness temperature depends on the surface temperature and emissivity two factors. In passive microwave remote sensing, the brightness temperature can be obtained by the microwave radiometer and emissivity is depend on the characteristics of object. Therefore, it is the most critical physical parameters in passive microwave remote sensing. In this paper, based on the basic microwave radiation transfer theory, to establish the bare surface layered soil emissivity model and calculated the soil emissivity into the final free space. The relationship between brightness temperature and soil moisture can given by soil emissivity.Combined with the soil dielectric model and the Q/H model by bare surface soil emissivity model,the relationship of the brightness temperature and soil moisture at the frequencies of 6.9 GHz, 10.65GHz, 18.7GHz and H and V polarization is simulated. In this study, Taklimakan Desert is taken as an example, some related important parameters were simulated. The retrievals of soil moisture are implemented. And the results are compared with the soil water products from the United States national snow and ice Centre (NSIDC). The RMSE shows that H polarization has good effect than the V polarization at different frequencies. Analysis the relation...
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