Abstract
Abstract. Near-surface soil moisture is one of the crucial variables in hydrological processes, which influences the exchange of water and energy fluxes at the land surface/atmosphere interface. Accurate estimate of the spatial and temporal variations of soil moisture is critical for numerous environmental studies. On the other hand, information of distributed soil moisture at large scale with reasonable spatial and temporal resolution is required for improving climatic and hydrologic modeling and prediction. The advent of hyperspectral imagery has allowed examination of continuous spectra not possible with isolated bands in multispectral imagery. In addition to high spectral resolution for individual band analyses, the contiguous narrow bands show characteristics of related absorption features, such as effects of strong absorptions on the band depths of adjacent absorptions. Our objective in this study was to develop a new spectral angle index to estimate soil moisture based on spectral region (350 and 2500 nm). In this paper, using spectral observations made by ASD Spectroradiometer for predicting soil moisture content, two soil indices were also investigated involving the Perpendicular Drought Index (PDI), NMDI (Normalized Multi-band Drought Index) indices. Correlation and regression analysis showed a high relationship between PDI and the soil moisture percent (R2 = 0.9537) and NMDI (R2 = 0.9335). Furthermore, we also simulated these data according to the spectral range of some sensors such as MODIS, ASTER, ALI and ETM+. Indices relevant these sensors have high correlation with soil moisture data. Finally, we proposed a new angle index which shows significant relationship between new angle index and the soil moisture percentages (R2 = 0.9432).angle index relevant bands 3, 4, 5, 6, 7 MODIS also showing high accuracy in estimation of soil moisture (R2 = 0.719).
Highlights
Soil moisture is the water that is held in the spaces between soil particles
Figure (10) shows that there is a significant relationship with a high correlation between this angle index and soil moisture (%)
The basis of the optical technique for soil moisture estimation rests on the connection between soil surface reflectance and moisture contents
Summary
Soil moisture is the water that is held in the spaces between soil particles. Surface soil moisture is one of the key variables in controlling the exchange of water and heat energy between land surface and atmosphere through evaporation and plant transpiration (Betts et al, 1996; Clark and Arritt, 1995).It is widely recognised as a key parameter in numerous environmental studies, including meteorology, hydrology, agriculture and climate change(Walker, 1999). As a result of the heterogeneity of soil properties, topography, land cover, evapotranspiration and precipitation, soil moisture, is highly variable both spatially and temporally (Engman, 1991; Wood et al, 1992; Walker, 1999). Satellite remote sensing offers a means of measuring soil moisture across a wide area continuously over time (Engman,1990), while techniques in the microwave and optical/IR frequency regimes have attracted more attention (Chauhan, 2003)
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