Retrieval Of Soil Moisture Status In China And Analysis Of Its Spatial And Temporal Distribution Characteristics

Soil moisture is basic information in researchs on agriculture, water resources, meteorology and ecology. It is also an important indicator in soil degradation monitoring and environment supervision. Doriving large-scalev soil moisture data using RS method can be of great support for exploration in these fields.The researches in this paper are part of the subject "Key technique researches on quantitative retrieval of ecology security relevant dements ". This work aims to conduct temporal soil moisture retrieval in China and explore its spatial and temporal distribution characteristics.In this research, after evaluation of all the models, TYDI (Temperature Vegetation Dryness Index) is selected for soil moisture evaluation in China. Analyses on the theories of TVDI reveal the affecting factors of TYDI method, these factors include solar radiation, air temperature, albedo, air density, surface emission, wind speed, etc. The affection of air temperature is discussed detailedly in this paper.In that the affection of air temperature is relevant to elevation, DEM is used in the correction of the effects of air temperature in soil moisture retrieval. Lapse rate and analysis of relation between derived data and field data arc used to determine the coefficient in correction. Compare of the TVD! derived before and after the correction shows that the TVDI acquired after DEM correction can better reflect the spatial distribution of soil moisture in China. The compare also reveals the relation beiwcen TVDI. and soil moisture is best when the soil water content is between 0.05-0.15g.cm^-3. As more than 90% pixels are located in this region, we consider TVDI a feasible method in soil moisture derivation.The year round soil moisture status is dorived using the DEM corrected TYDI. Conditions of multi-temporal Ts-NDVI space are analyzed and wet and dry edges of...