第10章4 流域数据获取-土壤水分遥感.ppt

影响精度的因素Factors affecting accuracy 植被覆盖 Vegetation cover Most important, dense vegetation (corn, forest) can obscure soil surface Greater effect at shorter λ 土壤特征 Soil properties Density and texture 表面粗糙度 Surface roughness Commonly 10 to 20% reduction in response range Density and roughness relatively constant 有关算法 An algorithm for merging SMAP radiometer and radar data for high resolution soil moisture retrieval - Das, N., Entekhabi, D., Njoku, E., IEEE-Transactions on Geoscience and Remote Sensing, In press. Download?File /files/smap2/0250_Das.pdf 4、可见光-近红外土壤水分遥感 Visible and near-infrared remote sensing Total Upwelling Radiance (Lt) Recorded by a Remote Sensing System over Exposed Soil is a Function of Electromagnetic Energy from Several Sources 光学遥感土壤水分 Optical Remote Sensing Soil Moisture 卫星接收辐射的构成 土壤特征 Soil Properties Spectral reflectance function of Soil texture, moisture, salinity, surface roughness, organic matter, iron oxide 光谱反射因素 Radiant energy may be reflected from the surface of the dry soil, or it penetrates into the soil particles, where it may be absorbed or scattered. Total reflectance from the dry soil is a function of specular reflectance and the internal volume reflectance. As soil moisture increases, each soil particle may be encapsulated with a thin membrane of capillary water. The interstitial spaces may also fill with water. The greater the amount of water in the soil, the greater the absorption of incident energy and the lower the soil reflectance. Reflectance from Dry versus Wet Soils Reflectance from Moist Sand and Clay Soils Higher moisture content in (a) sandy soil, and (b) clayey soil results in decreased reflectance throughout the visible and near-infrared region, especially in the water-absorption bands at 1.4, 1.9, and 2.7 mm. 湿度增加，可见近红外光谱反射降低 用植被估计土壤水分Estimating SM with vegetation Surface soil moisture correlation with sub-surface sm decreases with depth 随深度增加，表层土湿度与下层土湿度相关性降低 植被指数与根带土壤水分的关系 不同生长季土壤水分与NDVI的相关系数 Correlati